For many subjects you should know base quantity (measurement types) and their base/international units (the base units the measurements are measured in internationally). These are shown below:

- Length – Metre (m)
- Mass – Kilogram(Kg)
- Time – Seconds (s)
- Electric Current – Amperes/Amps (A)
- Temperature – Kelvin (K)
- Amount of substance – Moles (mol)

Make sure you learn these.

# Prefixes:

For super large or super small numbers we also use prefixes. For example, one thousand grams is called a **kilo**gram. The prefix here is **kilo** which is a multiplying factor of a thousand. A **kilo*** *is abbreviated to the letter **k**. For many courses you must learn the following prefixes off by heart. You should also know what each prefix abbreviation stands for. Below shows each prefix name – the abbreviation – and the multiplying factor.

- Femto = f = 10^-15
- Pico = p = 10^-12
- Nano = n = 10^-9
- Micro = μ = 10^-6
- milli = m = 10^-3
- Kilo = k = 10^3
- Mega = M = 10^6
- Giga = G = 10^9
- Tera = T = 10^12

Notice that some of the abbreviations have Lower and some Upper case- **Do not confuse the two.**

An example of using these prefixes:

3.9nA = 3.9 nano Amps = **3.9 x 10^-9 Amps**