thirteenth

UK: /ˌθɜː^rˈtiːnθ/ US: (thûr′tēnth′)

WordReference Random House Unabridged Dictionary of American English © 2025

thir•teenth  (thûr′tēnth′), adj. 

1. next after the twelfth;
   being the ordinal number for 13.
2. being one of 13 equal parts.

n. 

3. a thirteenth part, esp. of one (¹⁄₁₃).
4. the thirteenth member of a series.

• bef. 900; thirteen + -th²; replacing Middle English thrittenthe (see three, tenth), Old English thryttēotha (see tithe)

Collins Concise English Dictionary © HarperCollins Publishers::

thirteenth / ˈθɜːˈtiːnθ/ adjective

1. (usually prenominal) coming after the twelfth in numbering or counting order, position, time, etc; being the ordinal number of thirteen: often written 13th
2. (as noun): Friday the thirteenth

noun

1. one of 13 equal or nearly equal parts of something
2. (as modifier): a thirteenth part
3. the fraction equal to one divided by 13 ()
4. an interval of one octave plus a sixth
   See also interval5
5. short for thirteenth chord

WordReference Random House Learner's Dictionary of American English © 2025

thir•teen /ˈθɜrˈtin/   n. [countable]

1. a cardinal number, 10 plus 3.
2. a symbol for this number, as 13 or XIII.
3. a set of this many persons or things.

adj. [before a noun]

4. amounting to 13 in number.

thir•teenth, adj. 

WordReference Random House Unabridged Dictionary of American English © 2025

thir•teen  (thûr′tēn′), n. 

1. a cardinal number, 10 plus 3.
2. a symbol for this number, as 13 or XIII.
3. a set of this many persons or things.

adj. 

4. amounting to 13 in number.

• bef. 900; late Middle English thirttene, variant of Middle English thrittene, Old English thrēotēne; cognate with Dutch dertien, German dreizehn, Old Norse threttān. See three, -teen