# TABULA/samples/units

## What is meant by the word: units ?

The *units* of a given physical quantity is a standardized description of what the quantity is measured in.

Thus, if discussing distance, it is not enough for us to write down the number: `2`.
Our audience needs to know: *two – of what?*

- two metres?
- two centimetres?
- two kilometres?

If we mean *two kilometres*, there is a standard way of writing this down: ` 2 km `

- This standard is known as Système-Internationale (SI); and the units (
`km`) are called**SI-units**. - Other standards are possible, such as Imperial Units (the next most popular standard worldwide).

## SI Units and TABULA

TABULA works internally with SI-units. It can handle units in other standards of measurement, but only if such units are defined in terms of SI-units. Thus…

- one mile (1 mi) = 1.60934 km
- one pound (1 lb) = 0.45359237 kg

(These units are pre-defined in TABULA, along with hundreds of others. You don't need to look them up in a reference book and define them to TABULA yourself.)

**OBSERVATION:** *units* is a singular noun in this context.
It is short for: *scientific units*, and is * not* the plural of

*unit*.

(The word *unit[y]* means *one-ness*, referring to the value: `1`.

Examples of *units* are:

`kg`mass kilogram `mph`speed miles-per-hour `mi/h`speed miles-per-hour `m/s`speed metres-per-second `m·s⁻²`acceleration metres-per-second-every-second; metres-per-second-squared (correct SI units)