4.6 Apportionment methods - what does it mean that two quantities (votes and seats) are in proportion (proportional)

In general, proportion says that two ratios (or fractions) are equal. For example:

\[\frac{1}{2} = \frac{2}{4}\]

1-out-of-2 is equal to 2-out-of-4

The ratios are the same, so they are in proportion (are proportional). When things are in proportion, then their relative sizes are the same.