Reference

They gather commonly needed academic facts in one place — things like unit prefixes, conversion factors, notation conventions, and standard constants. They’re meant as quick lookups so you can check a value or symbol without hunting through a textbook.

SI prefixes scale a unit by powers of ten — for example kilo- means ×1,000, centi- means ÷100, milli- means ÷1,000, and mega- means ×1,000,000. They attach to any base unit, so a kilometre is 1,000 metres and a milligram is one-thousandth of a gram.

Scientific notation writes numbers as a value between 1 and 10 multiplied by a power of ten, such as 3.0 × 10⁸. It’s useful for very large or very small quantities and for keeping track of significant figures without writing long strings of zeros.

Accuracy is how close a measurement is to the true value, while precision is how close repeated measurements are to each other. A set of readings can be precise but not accurate if they cluster tightly around the wrong value, so good measurement aims for both.