Time:  As we have seen a single musical sound is represented by a note.  The most important things a written piece of music needs to tell you is the pitch and the duration, how long it lasts.  The pitch is determined by where it falls on the staff, the durations depends on the characteristics of the note itself.

note parts

All parts of the written note affect how long it lasts

Note length

note length

Half notes last half as long as a whole note.  Quarter notes are 1/4 as long, eighth notes 1/8 as long etc.

Note values are very much like fractions as is illustrated below

Whole and half note durations