名詞 fifteenth:

1. position 15 in a countable series of things

形容詞 fifteenth:

1. coming next after the fourteenth and just before the sixteenth in position
   同義詞：15th

1. The boat leaves Liverpool on the fifteenth, but before we set sail(for New York) I have to spend a few days in Scotland.
   船十五號離開利物浦，但是(開往紐約)之前，我得在蘇格蘭呆上幾天。
2. He traces his family back to about the fifteenth century.
   他把他的家世追溯到十五世紀(jì)前後。
3. Most students in this class are fifteen.
   這個班的大多數(shù)孩子都十五歲。

fif.teenth

n.（名詞）
The ordinal number matching the number 5 in a series.
第十五：在一系列中排在第十五的序數(shù)
One of 5 equal parts.
十五分之一

【引伸】
fifteenth.
adv.（副詞）
adj.（形容詞）