eleventh

elev·enth [eleventh elevenths] [ɪˈlevnθ] ; [ɪˈlevnθ] ordinal number, noun There are examples of how to use ordinal numbers at the entry for fifth.

Main entry: eleven_derived

Cambridge Advanced Learner's Dictionary

Cambridge Advanced Learner's Dictionary - 4th Edition

eleventh / ɪˈlev. ə nθ / ordinal number

11th written as a word:

Her birthday is on the eleventh ( of this month).

Collins COBUILD Advanced Learner’s English Dictionary

eleventh

[ɪle̱v(ə)nθ]
♦♦
ORD
The eleventh item in a series is the one that you count as number eleven.
We were working on the eleventh floor.

Merriam-Webster's Advanced Learner's Dictionary

Merriam-Webster's Advanced Learner's Dictionary:

eleven

elev·en /ɪˈlɛvən/ noun, pl -ens
1 [count] : the number 11
2 [count] : the eleventh in a set or series
• page eleven
• item/question number eleven
3 [noncount] : eleven o'clock
• I got home last night at eleven.
- eleven adj
• eleven turtles
- eleven pronoun
• Eleven (of them) were absent from the ceremony.
- elev·enth /ɪˈlɛvənɵ/ noun, pl -enths [count]
• one eleventh of the total
- eleventh adj
• the eleventh person in line
- eleventh adv
• He finished eleventh in the race.