sixth

I. sixth¹ /sɪksθ/ BrE AmE adjective
coming after five other things in a series:
her sixth birthday
the sixth century
—sixth pronoun:
Let’s have dinner on the sixth (=the sixth day of the month).

Oxford Advanced Learner's Dictionary

sixth

sixth [sixth sixths] ordinal number, noun [sɪksθ] [sɪksθ]

ordinal number

6th There are examples of how to use ordinal numbers at the entry for fifth.

noun

each of six equal parts of sth

Cambridge Advanced Learner's Dictionary

Cambridge Advanced Learner's Dictionary - 4th Edition

sixth / sɪksθ / ordinal number

A2 6th written as a word:

I have to return my library books on the sixth ( of July).

England were/came sixth in the 100 metres.

Collins COBUILD Advanced Learner’s English Dictionary

sixth

[sɪ̱ksθ]
♦♦
sixths
1) ORD The sixth item in a series is the one that you count as number six.
  ...the sixth round of the World Cup.
  ...the sixth of December.
2) FRACTION A sixth is one of six equal parts of something.
  The company yesterday shed a sixth of its workforce.
  ...five-sixths of a mile.

Merriam-Webster's Advanced Learner's Dictionary

Merriam-Webster's Advanced Learner's Dictionary:

sixth

²sixth adj : occupying the number six position in a series
• on the sixth day
• the book's sixth edition
• I finished in sixth place in the competition.
- sixth adv
• She finished sixth in the race.
• the nation's sixth largest city