Symphony No. 5 (Beethoven) is commonly referred to as Beeethoven's Fifth

A common term for 750 mL of hard liquor, approximately one fifth of a U.S. gallon.

In music theory:

A political term, fifth column

1st Battalion 5th Marines

Fifth force - a proposed force of nature in addition to the four known fundamental forces

Fifth disease - a contagious rash that spreads in school aged children

A Fifth-generation programming language

5 (Soft Machine album)

One fifth, a quintile, or 20% of a certain amount

In the United States, the Fifth Amendment to the United States Constitution especially as in the expression "Taking the Fifth".

A musical interval; specifically, a perfect fifth, diminished fifth or augmented fifth

A chord member separated from the chord's root by one of the above intervals

The dominant or fifth diatonic scale degree, and the chord built on it