fifteen-year-old
UK[ˌfɪfˈtiːn jɪər əʊld]US[ˌfɪfˈtiːn jɪr oʊld]
adj
being fifteen years of age
n
a person who is fifteen years old
Morpheme Breakdown
fifteen
year
old
fifteen
year
old
Etymology
the compound "fifteen-year-old" is a modern english construction built entirely from native old english elements. "fifteen" derives from the old english "fīftīene," a combination of "fīf" (five) and "tīene" (ten), following a common germanic pattern for forming teens. "year" comes from old english "gēar," related to time and cycles, while "old" originates from old english "eald," meaning aged or advanced in years. the hyphenated structure emerged as a grammatical convention to fuse these three distinct concepts—a specific number, a temporal unit, and a state of being—into a single, cohesive adjective or noun phrase that precisely denotes an age of fifteen years.
Analysis
Structure: fifteen + year + old
fifteen (old english; cardinal number), year (old english; unit of time), old (old english; adjective suffix indicating age)
Examples
she is a talented fifteen-year-old pianist.
the film is suitable for a fifteen-year-old audience.
my brother just became a fifteen-year-old last week.