The numerical size of an [[intervals|interval]] corresponds to the number of lines and spaces (or letter names) that it spans, ignoring any [[accidentals]]. When counting the number of lines and spaces between the notes of an interval, we include the first note in the count, starting at 1. Interval sizes are named using ordinal numbers (e.g. second, third, fourth, and so on) except for the **unison** (1) and the **octave** (8). **Example 1.** Interval sizes with names and numerical abbreviations. ![[example intervals sizes.png]]