- As an ordinal number, it means the third in a series or sequence. For example, "The third person in line is next to go."
- As a fraction, it means one divided by three. For example, "One-third of the pie is left."
- In music, the third is a musical interval consisting of two whole tones. It is also the name of the third note of a scale, which is always three steps from the tonic (the first note of the scale). For example, in the scale of C major, the third note is E.