fifteenth

UK: /ˌfɪfˈtiːnθ/ US: (fif′tēnth′)

WordReference Random House Unabridged Dictionary of American English © 2026

fif•teenth  (fif′tēnth′), adj. 

1. next after the fourteenth;
   being the ordinal number for 15.
2. being one of 15 equal parts.

n. 

3. a fifteenth part, esp. of one (¹⁄₁₅).
4. the fifteenth member of a series.
5. [Music.] the interval of two octaves.

• bef. 900; Middle English fiftenthe (see fifteen, -th²); replacing Middle English fiftethe, Old English fīftēotha

Collins Concise English Dictionary © HarperCollins Publishers::

fifteenth / ˈfɪfˈtiːnθ/ adjective

1. coming after the fourteenth in order, position, time, etc. Often written: 15th
2. (as noun): the fifteenth of the month

noun

1. one of 15 equal or nearly equal parts of something
2. (as modifier): a fifteenth part
3. the fraction equal to one divided by 15 ()
4. an interval of two octaves
5. one of two notes constituting such an interval in relation to the other, esp the one higher in pitch
6. an organ stop of diapason quality sounding a note two octaves higher than that normally produced by the key depressed; a two-foot stop

WordReference Random House Learner's Dictionary of American English © 2026

fif•teen /ˈfɪfˈtin/   n. [countable]

1. a cardinal number, ten plus five.
2. a symbol for this number, as 15 or XV.

adj. [before a noun]

3. amounting to 15 in number.

fif•teenth, adj., n. [countable]

WordReference Random House Unabridged Dictionary of American English © 2026

fif•teen  (fif′tēn′), n. 

1. a cardinal number, ten plus five.
2. a symbol for this number, as 15 or XV.
3. a set of this many persons or things.

adj. 

4. amounting to 15 in number.

• Middle English, Old English fiftene. See five, -teen bef. 900