Calculator Glossary

Plain-English definitions for every term you’ll encounter across our 153 calculators — APR, EMI, BMI, TDEE, ROI, VO2max, and 107 more. Each entry links to the calculators where the term is used.

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1RM (One-Rep Max): The heaviest weight you can lift for a single repetition with good form on a given exercise. Programs prescribe sets at percentages of 1RM (e.g. 5×5 at 80%) — the Epley and Brzycki formulas estimate 1RM from a sub-maximal set. See: One-Rep Max Calculator.

A

AGI (Adjusted Gross Income): Your total US income for the year minus “above-the-line” deductions like 401(k) contributions, HSA, and student-loan interest. AGI is the number tax brackets, IRA limits, and most credits are calculated against. See: Take-Home Pay Calculator, Tax Bracket Calculator.
Amortization: The schedule that splits each loan payment into principal and interest. Early payments are mostly interest; later payments are mostly principal — so the same monthly check chips away at the balance very differently across the term. See: Loan EMI Calculator, Mortgage Calculator.
AMT (Alternative Minimum Tax): A parallel US tax system that recalculates your liability after adding back certain preference items (most often ISO bargain element). You pay the higher of regular tax and AMT — common for tech employees who exercise ISOs. See: ISO/NSO Calculator.
APR (Annual Percentage Rate): The yearly cost of borrowing expressed as a percentage, including interest plus most lender fees. APR is always equal to or higher than the quoted note rate; comparing APRs (not rates) is the apples-to-apples way to shop a loan. See: Loan EMI Calculator, Mortgage Calculator, Credit Card Payoff Calculator.
APY (Annual Percentage Yield): The yearly return on a deposit account once compounding is included. APY > APR for the same nominal rate; the gap widens with more frequent compounding. See: Compound Interest Calculator.
ARM (Adjustable-Rate Mortgage): A mortgage whose rate is fixed for an introductory period (commonly 5, 7, or 10 years) and then resets periodically against an index plus a margin. Lower start rate, higher tail risk than a fixed-rate loan. See: Mortgage Calculator, Mortgage Refinance Calculator.
ARR (Annual Recurring Revenue): Predictable subscription revenue normalized to a yearly figure (MRR × 12). The headline metric for SaaS valuation; one-time fees and usage overage do not count. See: SaaS Pricing Tier Calculator.
Asset Allocation: The mix of stocks, bonds, cash, and alternatives in a portfolio. Drives roughly 90% of long-term return variance — picking allocation correctly matters far more than picking individual stocks. See: Retirement Savings Calculator, FIRE Monte Carlo Calculator.

B

Base + Variable Pay: A compensation structure splitting cash into a guaranteed base salary and an at-risk variable component (commission, bonus, MBO). Common in sales; the OTE is base plus variable assuming 100% of target. See: Job Offer Comparison Calculator.
BMI (Body Mass Index): Weight in kilograms divided by height in meters squared. WHO bands: under 18.5 underweight, 18.5-24.9 healthy, 25-29.9 overweight, 30+ obese. A population screen, not a body-composition tool — muscular builds register high without excess fat. See: BMI Calculator, Ideal Weight Calculator.
BMR (Basal Metabolic Rate): The calories you burn at complete rest — heartbeat, breathing, basic cell maintenance. Estimated by the Mifflin-St Jeor equation; roughly 60-70% of total daily energy expenditure for a sedentary adult. See: Calorie TDEE Calculator.
Body Fat Percentage: Fat mass as a share of total body mass. Healthy ranges differ by sex: roughly 10-20% for men, 18-28% for women. Estimated cheaply via the US Navy circumference method or directly via DEXA / hydrostatic. See: Body Fat Calculator.
Bonus Tax: How the IRS taxes supplemental wages. Federal default withholds at a flat 22% (37% above $1M YTD), but the bonus is still taxed at your true marginal rate at year-end — over-withhold gets refunded, under-withhold becomes an April bill. See: Bonus Tax Calculator.
BTU (British Thermal Unit): The energy needed to raise one pound of water by 1°F. Used to size HVAC equipment — a typical US home needs roughly 20-25 BTU/sq ft of cooling capacity, adjusted for climate, insulation, and shading. See: AC Sizing Cost Calculator.
Burn Rate: Net cash a startup spends per month (gross burn = total expenses; net burn = expenses minus revenue). Combined with cash on hand, gives runway — the months remaining before fundraising or breakeven becomes existential. See: Business calculators.

C

CAC (Customer Acquisition Cost): Sales + marketing spend divided by new customers won. Paired with LTV (lifetime value) — healthy SaaS targets LTV/CAC of 3 or higher with payback under 12-18 months. See: SaaS Pricing Tier Calculator, Ad ROAS Predictor.
CAGR (Compound Annual Growth Rate): The constant yearly rate that grows a starting value to an ending value over N years. CAGR = (end/start)^(1/N) - 1. Smooths out year-by-year volatility into a single comparable number. See: Investment ROI Calculator, Compound Interest Calculator.
Calorie Deficit / Surplus: Eating fewer calories than you burn (deficit, drives fat loss) or more than you burn (surplus, drives muscle gain). A 500 kcal/day deficit yields roughly 0.45 kg / 1 lb of fat loss per week. See: Calorie TDEE Calculator, Macros Cutting/Bulking Calculator.
Carbon Footprint: Total greenhouse-gas emissions (in CO₂e) caused directly and indirectly by a person, household, or activity over a year. US per-capita average is roughly 16 tonnes; the Paris-aligned target is closer to 2. See: Carbon Footprint Calculator, Flight Emissions Calculator.
Churn: The rate at which customers cancel. Monthly churn of 5% sounds small but compounds to roughly 46% annual churn — most subscription businesses fail because churn outruns acquisition, not because acquisition is too slow. See: SaaS Pricing Tier Calculator.
Cold Start (AI): Latency added when the first request to a model server has to load weights into memory. On serverless GPU platforms this can add 5-30 seconds; persistent inference instances trade higher idle cost for sub-second latency. See: GPU Rental vs API Calculator.
Compound Interest: Interest earned on both the principal and the previously earned interest. The shape is exponential, not linear — over 30 years at 7% annual return, 80%+ of the ending balance is compound growth, not contributions. See: Compound Interest Calculator, Retirement Savings Calculator.
Context Window: The maximum number of tokens an LLM can attend to in a single request (input + output). Pricing scales linearly with context length on most providers — keeping prompts concise is the cheapest optimization available. See: Token Context Window Calculator, AI Model Cost Calculator.
COP (Coefficient of Performance): Heat-pump efficiency: heat moved divided by electrical energy used. A COP of 3 means 3 kWh of heat for every 1 kWh of electricity — three times more efficient than resistive electric heat. See: Heat Pump Payback Calculator.

D

DTI (Debt-to-Income Ratio): Total monthly debt payments divided by gross monthly income. Lenders cap conventional mortgages at roughly 43-45% DTI; under 36% is the comfortable-borrower bar. See: Can I Afford Calculator, House Affordability Calculator.

E

EDD (Estimated Due Date): The projected date of birth — typically calculated as 280 days (40 weeks) from the last menstrual period via Naegele’s rule. Only about 4-5% of babies arrive on the EDD; the 37-42 week window is normal. See: Pregnancy Due Date Calculator, Pregnancy Week by Week Calculator.
Effective Tax Rate: Total tax paid divided by total taxable income. Always lower than your marginal rate because progressive brackets only apply the top rate to the top slice of income. See: Tax Bracket Calculator, Take-Home Pay Calculator.
Embedding: A dense vector representation of text, image, or other input — the geometry an LLM uses to compare meaning. Storing embeddings in a vector DB powers semantic search and most RAG pipelines. See: Fine-tune vs RAG Calculator.
EMI (Equated Monthly Installment): A fixed monthly loan payment that covers principal plus interest. Same number every month for the term; the split between principal and interest shifts each cycle as the balance falls. See: Loan EMI Calculator, Mortgage Calculator.
Epoch (Unix): Seconds elapsed since 1970-01-01 00:00:00 UTC. Programmers store and compare timestamps in epoch form to avoid timezone and DST ambiguity. See: Time Zone Converter.
Escrow (Mortgage): A lender-held account that bundles property tax and homeowners insurance into the monthly payment, paid out by the servicer when bills come due. Required while LTV is above 80% on most US mortgages. See: Mortgage Calculator, PMI Removal Calculator.
Estimated Tax (Quarterly): Pay-as-you-go tax payments for income without withholding (1099, interest, capital gains). US deadlines: Apr 15, Jun 15, Sep 15, Jan 15. Underpayment triggers Form 2210 penalties. See: Quarterly Estimated Tax Calculator.

F

FICA (Federal Insurance Contributions Act): US payroll tax funding Social Security (6.2% on wages up to the annual cap) and Medicare (1.45%, with a 0.9% surcharge above $200k). Employers match both — self-employed pay both halves as SECA. See: Take-Home Pay Calculator, W-2 vs 1099 Calculator.
Fine-tuning: Continuing the training of a base model on a domain-specific dataset to bake in style, terminology, or task accuracy. Typically beats prompt engineering for narrow tasks; loses to RAG when the data must stay current. See: Fine-tune vs RAG Calculator.
FIRE (Financial Independence, Retire Early): A movement that targets a portfolio of roughly 25× annual expenses (the “4% rule”) so that work becomes optional. Sub-flavors: Lean FIRE, Fat FIRE, Coast FIRE, Barista FIRE. See: FIRE Monte Carlo Calculator, Retirement Savings Calculator.
Fixed-Rate Mortgage: A mortgage whose interest rate is locked for the entire term (commonly 15 or 30 years). Higher start rate than an ARM but zero rate-reset risk. See: Mortgage Calculator, Mortgage Refinance Calculator.

G

GCD (Greatest Common Divisor): The largest integer that divides two numbers without remainder. GCD(12, 18) = 6. Used to reduce fractions and ratios to lowest terms. See: Fraction Calculator, Ratio Calculator.
Gestational Age: Pregnancy duration measured from the first day of the last menstrual period (LMP), not from conception. Adds roughly two weeks to fetal age — a 40-week gestation is a 38-week embryo/fetus. See: Pregnancy Week by Week Calculator, Pregnancy Due Date Calculator.

H

Heat Pump: An electric HVAC system that moves heat rather than generating it — heating in winter, cooling in summer. Modern cold-climate models hold rated capacity down to -15°F and beat gas furnaces on lifetime cost in most US climates. See: Heat Pump Payback Calculator.
HRZ (Heart Rate Zone): Training-intensity bands defined as percentages of max heart rate (commonly 220 minus age). Zone 2 (60-70%) builds the aerobic base; zone 4-5 (80%+) drives VO2max. See: Heart Rate Zone Calculator, VO2max Target Calculator.

I

IANA Time Zone: Canonical time-zone identifiers like “America/New_York” or “Asia/Karachi” maintained by the IANA tz database. Encode DST rules historically — using them avoids the off-by-one bugs that plague GMT-offset arithmetic. See: Time Zone Converter.
ICE (Internal Combustion Engine): A traditional gasoline or diesel engine. Compared with EVs, ICE vehicles have lower sticker price but higher fuel and maintenance cost over a typical 8-12 year ownership horizon. See: EV vs Gas Cost Calculator, EV vs ICE TCO Calculator.
Inference: Running a trained model on new input to produce an output (vs training, which updates weights). Inference cost is usually the dominant lifetime spend on production ML — training is one-time, inference scales with usage. See: AI Agent Run Cost Calculator, GPU Rental vs API Calculator.
IRR (Internal Rate of Return): The annualized return that makes the net present value of a set of cash flows zero. Comparable across investments with different shapes; only valid when cash-flow signs change once. See: Investment ROI Calculator, Property Flip ROI Calculator.
ISO (Incentive Stock Option): A US tax-favored stock option for employees. Holding for 2 years from grant + 1 year from exercise yields long-term-capital-gains treatment on the spread — but the bargain element is an AMT preference item. See: ISO/NSO Calculator.
ISO 8601: The international date-time format YYYY-MM-DD or YYYY-MM-DDTHH:mm:ssZ. Sortable as plain text and unambiguous across locales — the only date format you should store. See: Age Calculator.
Itemized Deduction: US tax filing path that lists individual deductible expenses (mortgage interest, SALT capped at $10k, charity, medical above 7.5% AGI). Worth doing only when the total exceeds the standard deduction. See: Tax Bracket Calculator.

J

Julian Date: Days elapsed since noon UTC on January 1, 4713 BC — a continuous count used by astronomers and some legacy systems. Today’s Julian date is roughly 2,460,000. See: Days Between Dates Calculator.

K

kWh (Kilowatt-hour): The energy used by a 1,000-watt appliance running for one hour. The standard billing unit on US electricity bills; a typical US home uses roughly 900 kWh per month. See: Electricity Bill Optimizer, Solar ROI Calculator.

L

Latency: Time between request and first response token. For interactive UIs the “feels instant” bar is roughly 200 ms to first token; longer than ~3 s and users assume the page is broken. See: GPU Rental vs API Calculator.
LCM (Least Common Multiple): The smallest integer that is a multiple of two given numbers. LCM(4, 6) = 12. Used to find common denominators for fraction arithmetic and to align repeating cycles. See: Fraction Calculator.
Lean Mass: Body mass minus fat mass — muscle, bone, organs, water. The denominator for the protein-per-kg target most lifters and athletes track. See: Body Fat Calculator, Protein Intake Calculator.
Leap Year: Years divisible by 4 (but not 100, unless also by 400) carry an extra day, February 29. The rule keeps the calendar year synced with the solar year; ignoring it causes off-by-one bugs in age + duration math. See: Age Calculator, Days Between Dates Calculator.
LMP (Last Menstrual Period): First day of the last period before pregnancy was detected. The reference date for Naegele’s rule, gestational age, and the standard 40-week due-date math. See: Pregnancy Due Date Calculator, Ovulation Calculator.
LTV (Loan-to-Value): Loan balance divided by appraised property value. Above 80% LTV most US lenders require PMI; reaching 78% (by amortization or reappraisal) lets you cancel it. See: Mortgage Calculator, PMI Removal Calculator.
LTV/CAC Ratio: Customer lifetime value divided by acquisition cost. SaaS rule of thumb: 3+ is healthy, 1 means you are buying revenue at par, below 1 means you lose money on every customer won. See: SaaS Pricing Tier Calculator, Ad ROAS Predictor.
Luteal Phase: The roughly 14-day window between ovulation and the next period. Length is the most consistent component of the cycle — variation across cycles usually comes from the follicular phase, not the luteal. See: Ovulation Calculator.

M

Macros (Macronutrients): The three energy-yielding nutrients: protein (4 kcal/g), carbohydrate (4 kcal/g), and fat (9 kcal/g). Setting macro targets shapes body composition far more than calorie count alone. See: Macro Calculator, Macros Cutting/Bulking Calculator.
MAGI (Modified Adjusted Gross Income): AGI plus certain add-backs (foreign earned income, student-loan interest, etc.). Used by the IRS to phase out Roth IRA eligibility, premium tax credits, and several other deductions. See: Roth vs Traditional 401(k).
Marginal Tax Rate: The rate paid on the next dollar of income. Determines the after-tax value of bonuses, overtime, and tax-deferred contributions; always higher than the effective rate in a progressive system. See: Tax Bracket Calculator, Bonus Tax Calculator.
Mean / Median / Mode: Three flavors of “average.” Mean = sum divided by count (sensitive to outliers). Median = middle value (robust). Mode = most frequent value. Income data is usually reported as median because the mean is skewed by top earners. See: Average Calculator.
METs (Metabolic Equivalents): A multiple of resting metabolic rate. Walking is roughly 3 METs, running 8 minute miles is 12 METs. Multiply METs by body weight (kg) and hours to estimate calories burned in an activity. See: Exercise Equivalent Calculator, Running Pace Calculator.
MoE (Mixture of Experts): An LLM architecture that routes each token to a small subset of expert sub-networks rather than the full model. Lets a 200B-parameter model run with 30B-parameter inference cost — strong cost-per-quality at large scale. See: AI Model Cost Calculator.
MPGe (Miles per Gallon Equivalent): EV efficiency expressed in gasoline-equivalent terms — 33.7 kWh equals one gallon of gas by energy content. Lets you compare EV efficiency directly with ICE MPG. See: EV vs Gas Cost Calculator, EV vs ICE TCO Calculator.
MRR (Monthly Recurring Revenue): Predictable subscription revenue normalized to a monthly figure. Composed of new MRR, expansion MRR (upgrades), contraction MRR (downgrades), and churned MRR. See: SaaS Pricing Tier Calculator.

N

Naegele’s Rule: The classic obstetric formula: estimated due date = LMP + 1 year - 3 months + 7 days, equivalent to 280 days from LMP. Assumes a 28-day cycle with ovulation on day 14. See: Pregnancy Due Date Calculator.
NPS (Net Promoter Score): Percentage of promoters (9-10 on a 0-10 “would you recommend” survey) minus percentage of detractors (0-6). Range -100 to +100; SaaS median is around +30. See: Business calculators.
NPV (Net Present Value): Sum of future cash flows discounted to today at a chosen rate. Positive NPV means the project beats the discount rate; the standard test for capital allocation. See: Investment ROI Calculator.
NSO (Non-Qualified Stock Option): A stock option without ISO tax treatment. Spread at exercise is taxed as ordinary income (W-2 wage); subsequent gain is capital. Simpler than ISOs but less tax-favored. See: ISO/NSO Calculator.

O

Origination Fee: Up-front lender fee for processing a loan, typically 0.5-1% of principal on US mortgages. Rolls into the APR — ignored when comparing rates alone, captured when comparing APR. See: Mortgage Calculator, Loan EMI Calculator.
OTE (On-Target Earnings): Total expected pay assuming 100% of variable targets hit — base salary plus full commission/bonus. Sales offers are usually quoted at OTE; the realized number is often 60-90% in year one. See: Job Offer Comparison Calculator, Salary Negotiation Counter.
Ovulation: Release of an egg from the ovary, typically around day 14 of a 28-day cycle. The fertile window is roughly the five days before ovulation plus the day of, since sperm survive longer than the egg. See: Ovulation Calculator.

P

P&I (Principal & Interest): The portion of a mortgage payment that pays down the loan and the interest charge — excludes property tax and insurance. Usually 60-80% of the total monthly cost on a US mortgage. See: Mortgage Calculator.
Percentage: A fraction expressed per hundred — 25% means 25/100 or 0.25. Useful for comparing across different bases; deceptively easy to misuse when comparing two percentages computed against different denominators. See: Percentage Calculator, Discount Calculator.
Percentage Change: (New - Old) / Old × 100. Going from 50 to 75 is a +50% change; 75 to 50 is a -33.3% change — directional asymmetry trips up most stock-return reporting. See: Percentage Calculator.
PITI (Principal, Interest, Taxes, Insurance): The full monthly housing payment on an escrowed mortgage. Lenders use PITI (not P&I alone) when computing housing-cost ratio and DTI. See: Mortgage Calculator, Can I Afford Calculator.
PMI (Private Mortgage Insurance): An insurance premium charged on US conventional mortgages with LTV above 80%, protecting the lender (not the borrower) if you default. Typically 0.3-1.5% of loan balance per year. See: PMI Removal Calculator, Mortgage Calculator.
Principal: The original amount borrowed — or the current outstanding balance after some has been paid down. Interest is always charged on the current principal, which is why early-loan payments feel mostly like interest. See: Loan EMI Calculator, Mortgage Calculator.
Proportion: An equality between two ratios, e.g. 2:3 = 4:6. Solving proportions is the basis for unit conversion, recipe scaling, and most map-scale arithmetic. See: Ratio Calculator, Unit Converter.

R

R-Value: A material’s resistance to heat flow per inch of thickness. R-19 batt insulation is a typical US wall standard; R-49 is a typical attic standard. Higher = better insulator, lower utility bill. See: Home Insulation ROI Calculator.
RAG (Retrieval-Augmented Generation): An LLM pattern that retrieves relevant documents from a vector store and stuffs them into the prompt before generation. Beats fine-tuning when the underlying knowledge changes faster than you want to retrain. See: Fine-tune vs RAG Calculator.
Ratio: A relationship between two quantities, written a:b. Reduce by dividing both sides by their GCD — 12:18 simplifies to 2:3. See: Ratio Calculator.
Rebalancing: Selling overweight assets and buying underweight ones to restore target allocation. Typically done annually or when any asset drifts more than 5 percentage points from target. Forces “sell high, buy low” mechanically. See: Retirement Savings Calculator.
Refinance: Replacing an existing mortgage with a new one — usually for a lower rate, a different term, or to cash out equity. Worth doing when rate savings cover closing costs within the planned ownership horizon. See: Mortgage Refinance Calculator.
RHR (Resting Heart Rate): Heart rate measured at full rest, typically first thing in the morning. Healthy adults sit at roughly 60-100 bpm; trained endurance athletes often run in the 40s. A trend up is a stronger fitness signal than a single reading. See: Heart Rate Zone Calculator.
ROI (Return on Investment): (Gain - Cost) / Cost × 100. Simple and comparable across categories, but ignores time — a 50% ROI in 1 year is very different from a 50% ROI in 10 years. Use CAGR or IRR when timing matters. See: Investment ROI Calculator, Ad ROAS Predictor.
RPE (Rate of Perceived Exertion): A 1-10 (or Borg 6-20) scale rating how hard a set or interval feels. RPE 8 means “2 reps left in the tank”; RPE 10 is true failure. Used as a substitute for strict %1RM programming. See: One-Rep Max Calculator.
RPM (Requests per Minute): API rate-limit unit — the number of requests per minute a key is allowed before throttling. Most LLM providers also enforce TPM (tokens per minute), and the lower of the two binds. See: AI Model Cost Calculator.
RSU (Restricted Stock Unit): Company stock granted to employees that vests over time (typically 4 years with a 1-year cliff). Vested shares are taxed as ordinary income at vest; subsequent gain is capital. See: RSU Tax Calculator, Job Offer Comparison Calculator.
Runway: Months of operation remaining at current burn rate, given current cash. The single most important number for an unprofitable startup; below 6 months and fundraising becomes a survival exercise instead of a strategic one. See: Should I Quit Job — Runway Calculator.

S

Scientific Notation: Writing a number as m × 10^n with 1 ≤ |m| < 10. 6.02 × 10²³ is Avogadro’s number — far more readable than 23 trailing zeros and computationally stable in floating point. See: Scientific Notation Calculator.
SECA (Self-Employment Contributions Act): The self-employed equivalent of FICA. You pay both the employer and employee halves — 15.3% on the first $168,600 (2024 cap) of net earnings, then 2.9% Medicare with no cap. See: W-2 vs 1099 Calculator, Freelance Rate Calculator.
SEER (Seasonal Energy Efficiency Ratio): Cooling output (BTU) divided by electrical input (Wh) over a typical cooling season. SEER 14 is the US minimum; SEER 20+ is high efficiency. Replaces older EER for residential AC units. See: AC Sizing Cost Calculator.
Sharpe Ratio: Excess return over the risk-free rate divided by standard deviation. Above 1 is good, above 2 is great. Penalizes return volatility — high Sharpe means smoother ride per unit of return. See: FIRE Monte Carlo Calculator.
Significant Figures: Digits in a number that carry meaningful precision. 0.00450 has three sig figs; trailing zeros after a decimal count. Multiplication and division results round to the input with the fewest sig figs. See: Scientific Notation Calculator.
Solar Payback: Years needed for cumulative electricity-bill savings to repay the net cost of a rooftop PV system (after federal ITC and state incentives). Typical US payback is 6-12 years for systems sized to annual consumption. See: Solar ROI Calculator.
Standard Deduction: A fixed deduction from US taxable income — $14,600 single, $29,200 married filing jointly for tax year 2024. About 90% of US filers take it instead of itemizing. See: Tax Bracket Calculator.
Standard Deviation: Average distance from the mean — the standard measure of spread. For normally distributed data, ~68% of values fall within one standard deviation of the mean, ~95% within two. See: Average Calculator, FIRE Monte Carlo Calculator.
Stock-Grant Cliff: An equity-vesting feature where nothing vests until a minimum tenure (typically 1 year) is reached, then a chunk vests at once. Drives the “don’t leave before month 12” calculus on most tech offers. See: Job Offer Comparison Calculator.

T

Tax Bracket: An income range taxed at a specific marginal rate. The US system has 7 federal brackets (10/12/22/24/32/35/37 in 2024); only the income inside each band pays that band’s rate. See: Tax Bracket Calculator.
TDEE (Total Daily Energy Expenditure): BMR multiplied by an activity factor (1.2 sedentary up to ~1.9 very active). The maintenance calorie target — eat below for fat loss, above for muscle gain. See: Calorie TDEE Calculator, Macros Cutting/Bulking Calculator.
Term (Loan): The number of months or years over which a loan is repaid. Longer term = lower monthly payment but more total interest paid; the trade-off is roughly 30-50% more lifetime interest going from a 15- to a 30-year mortgage. See: Loan EMI Calculator, Mortgage Calculator.
Time Zone Offset: The difference between local clock time and UTC, e.g. America/Los_Angeles is UTC-08:00 in winter and UTC-07:00 in summer. Always store timestamps as UTC and convert at display time. See: Time Zone Converter.
Token (LLM): The unit an LLM reads and writes — roughly 0.75 English words on average, but punctuation, code, and non-Latin scripts can be much denser. Pricing on every major LLM API is per million input + output tokens. See: Token Context Window Calculator, AI Model Cost Calculator, API Token Cost Calculator.
Trimester: One of the three roughly 13-week stages of pregnancy. First (weeks 1-13), second (14-26), third (27-birth). Risk profile, fetal milestones, and prenatal-care cadence shift across each. See: Pregnancy Week by Week Calculator.

U

UTC (Coordinated Universal Time): The primary time standard, equivalent to GMT for civilian purposes but defined by atomic clocks. The reference point all IANA time zones are offset against; never observes daylight saving. See: Time Zone Converter.

V

Visceral Fat: Fat stored around abdominal organs (liver, pancreas, intestines), distinct from subcutaneous fat just under the skin. Visceral excess is the strongest body-composition predictor of cardiovascular and metabolic disease. See: Body Fat Calculator, Biological Age Calculator.
VO2max: Maximum oxygen uptake during intense exercise, in mL/kg/min. The strongest single predictor of all-cause mortality after age and sex; trainable in most people by 15-25% over 6-12 months of structured aerobic work. See: VO2max Target Calculator, Biological Age Calculator.

W

1099: US tax form for non-employee compensation (1099-NEC for contractors) and other reportable income (interest, dividends, brokerage proceeds). 1099 income is responsible for both halves of FICA via SECA. See: W-2 vs 1099 Calculator, Freelance Rate Calculator, Quarterly Estimated Tax Calculator.
W-2: The US wage-and-tax statement issued each January by employers to employees. Reports gross wages, federal/state/FICA withholding, and 401(k) and health-insurance deductions for the prior calendar year. See: Take-Home Pay Calculator, W-2 vs 1099 Calculator.
Withdrawal Rate (Safe): The annual percentage of a retirement portfolio you can spend without running out over a multi-decade horizon. Trinity-study default is 4% inflation-adjusted; recent updated work argues 3-3.3% in low-real-rate regimes. See: FIRE Monte Carlo Calculator, Retirement Savings Calculator.
Withholding: Tax taken out of each paycheck and remitted to tax authorities by your employer. Set via Form W-4 (US); under-withholding triggers an April bill plus possible underpayment penalty. See: Take-Home Pay Calculator, Bonus Tax Calculator.