What the numbers are called, and what they mean

Amortisation is the schedule that splits a loan into equal repayments, each covering that period's interest plus a growing slice of principal until the balance reaches zero.

APR — the annual percentage rate — expresses the yearly cost of borrowing including fees and charges, so loans with different fee structures can be compared on a single number.

Aspect ratio is the proportional relationship between width and height — 16:9 means 16 units of width for every 9 of height, whatever the actual size.

Basal metabolic rate (BMR) is the energy the body uses at complete rest to run organs, breathing and circulation — typically 60–70% of daily energy use.

A base unit is the single reference unit a conversion passes through — metres for length, kilograms for mass — so any unit converts to any other without drift.

Body mass index (BMI) is weight in kilograms divided by height in metres squared; for adults, 18.5 to 24.9 is classified as the healthy weight range.

A business day is a weekday that is not a public holiday, so a deadline counted in business days skips weekends and the holidays of the relevant jurisdiction.

Degrees Celsius is a temperature scale with water freezing at 0 °C and boiling at 100 °C; Fahrenheit converts as (C × 9/5) + 32.

Compound interest is interest calculated on the balance plus interest already added, so savings grow faster than with simple interest charged only on the original amount.

GST is a goods and services tax added to most sales — 10% in Australia, 15% in New Zealand — so a GST-inclusive price is the base price multiplied by 1.10 or 1.15.

Lean body mass is everything in the body that is not fat — muscle, bone, organs and water — and it drives most of the body's resting energy use.

A leap year has 366 days, adding 29 February so the calendar stays aligned with Earth's orbit; years divisible by 4 are leap years, except centuries not divisible by 400.

Loan-to-value ratio (LVR) is the loan amount divided by the property's value: a $400,000 loan on a $500,000 home is an 80% LVR.

The median is the middle value of a sorted list — half the values sit below it and half above — which makes it resistant to outliers that pull an average.

A percentage point is the arithmetic difference between two percentages: a rate moving from 4% to 6% has risen by 2 percentage points, which is a 50% increase.

The principal is the amount you borrow, or the part of each repayment that reduces the balance rather than paying interest. Interest is charged on whatever principal is still outstanding.

Real return is an investment's return after inflation — the change in what your money can actually buy. A 5% return with 3% inflation is about 2% real.

Significant figures are the digits in a measurement that carry real precision — 0.004560 has four — and they set how precisely a result should be reported.

Standard deviation measures how far values typically sit from their mean; in a normal distribution about 68% of values fall within one standard deviation and 95% within two.

Superannuation is Australia's compulsory retirement savings system: employers pay a percentage of your salary into a fund, invested and taxed concessionally until retirement.

Total daily energy expenditure (TDEE) is everything you burn in a day: resting metabolism, the energy cost of digesting food, exercise and all incidental movement.

Unit price is the cost per standard measure — per 100 g, per litre, per item — so packs of different sizes can be compared like for like.