• One fifth, a quintile, or 20% of a certain amount
• The fifth in a series, or four after the first
• 1st Battalion 5th Marines
• In the United States, the Fifth Amendment to the United States Constitution especially as in the expression "Taking the Fifth".
• Fifth (Stargate), a robotic character in the television series Stargate SG-1
• A Fifth-generation programming language
• Symphony No. 5 (Beethoven) is commonly referred to as Beethoven's Fifth
• 5 (Soft Machine album)
• A common term for 750 ml of hard liquor, approximately one fifth of a U.S. gallon.
• A political term, fifth column
• Fifth disease - a contagious rash that spreads in school aged children
• Fifth force - a proposed force of nature in addition to the four known fundamental forces

In music theory:

• 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