fifteen

fifteen — number

1. the number that comes after fourteen and before sixteen in a counting sequence;

1.numberA1
Definition

the number that comes after fourteen and before sixteen in a counting sequence; written as 15 in numerals.

Example

Romi is fifteen years old and just started high school.

age: be + number + years old

The art class has fifteen students this semester.

quantity: number + plural noun

Usage Note

In formal writing, spell out fifteen up to the number ninety-nine. Use numerals (15) for dates, times, and statistics.

Common Mistakes

Fiveteen
fifteen
learners often add an extra 'e' after the 'v' by analogy with 'five'.
She is fifty years old.' (for age 15)
She is fifteen years old.
the -ty endings (fifty = 50) and -teen endings (fifteen = 15) are easily confused by learners.

fifteen — noun

Word family

  • fifteenth
    adjectiveA2
  • fifteenth
    nounB1
  • fifteen-year-old
    adjectiveA2
  • fifteen-year-old
    nounA2

Synonym discussion

Sense: number/1

Fifteen is the cardinal number (the quantity itself: 'there are fifteen chairs'), while fifteenth is the ordinal, used for position in a sequence ('the fifteenth chapter', 'her fifteenth birthday'). A fifteen-year-old is a noun or adjective describing a person of that age ('a class of fifteen-year-olds'). Unlike fifteen, which is a pure number, fifteen-year-old functions as a compound modifier and takes hyphens. In everyday use, learners need only distinguish cardinal fifteen (quantity) from ordinal fifteenth (position) — a distinction shared with all English number words.

fifteenfifteenthfifteen-year-old

Common collocations

Nouns

  • fifteen years
  • fifteen minutes
  • fifteen dollars
  • fifteen students

Phrases

  • fifteen years old
  • fifteen minutes past
  • a quarter past fifteen

Prepositions

  • at fifteen
  • by fifteen
  • over fifteen

Etymology

Old EnglishMiddle EnglishEnglish

Fifteen comes from Old English fīftīene, a combination of fīf (five) and tīene (ten). The same structure appears across Germanic languages: German fünfzehn, Dutch vijftien, and Old Norse fimmtán. The modern spelling settled as 'fifteen' in Middle English, replacing earlier forms like 'fiftyne'.