The following is a list of idioms about ordinal numbers (first, second, and so on) and multiplicative numbers, or what the late English-usage expert Henry Watson Fowler called numeral adverbs (once, twice, and so on). (Because I have already devoted an entire post to idioms that include first, I’ve omitted them here.)
1. bottom of the ninth: the last minute, from the last segment of the last inning of a baseball game
2. break the fourth wall: speaking directly to the audience during a theatrical performance (or, by extension, a film or a television program)
3. cheap at twice the price: exceedingly inexpensive
4. don’t think twice: don’t concern yourself about it
5. eleventh hour: the last minute
6. even a stopped clock is right twice a day: someone who is usually mistaken can be correct on rare occasions
7. fifth column: collaborators supporting would-be invaders from within a country
8. fool me once, shame on you; fool me twice, shame on me: a proverb expressing that one should be wary of the intentions of someone who has tricked one before
9. for once: on this particular occasion
10. Fourth Estate: journalists as a group (originally, a reference to the press in counterpoint to three other major demographic groups: the clergy, the nobility, and the common people)
11. give (one) the once-over: examine with interest
12–13. if I’ve told you once, I’ve told you a hundred/thousand times: a phrase expressing, with exaggeration, that one has repeatedly referred to something
14. lightning never strikes (the same place) twice: an unusual occurrence that has happened before won’t happen again
15. once and for all: permanently
16. once bitten, twice shy: a proverb expressing that one’s inclination is to avoid people who, or things, that have hurt them
17. once in a blue moon: very rarely
18. once in a lifetime: said of something likely to occur only once during one’s life
19. once over lightly: quickly
20. once upon a time: once in the past (used often as the beginning of a fairy tale to express that the story occurred long ago)
21. opportunity knocks but once: a proverb expressing that one may have only one chance to take advantage of an opportunity
22–23. plead/take the fifth: said humorously in response to a request for provocative information when one does not want to reveal it (a reference to the Fifth Amendment to the U.S. Constitution, which protects citizens against self-incrimination)
24. second banana: someone who plays a secondary role (from show business slang for a supporting comedian)
25. second best: something not as good as the thing desired
26. second chance: another opportunity
27. second childhood: a period later in life marked by renewed interest in things of interest to a child or by reduced mental capacity
28. second class: inferior, as in references to travel accommodations or disadvantaged citizens
29. second fiddle: one who plays, or is perceived to play, a subordinate role (from an informal reference to violinists in a music ensemble who are not the principal violinist)
30. second-guess: predict another’s action or decision
31. secondhand: as an adjective, not original, or previously owned; as an adverb, indirectly, or obtained from another
32. second nature: said of a behavior or habit that one seems to have been born with
33. second sight: clairvoyance, or the supposed ability to see something happening elsewhere or in the future
34. second thought: a reference to changing one’s mind, as in the phrase “on second thought” or to be inclined to do so, as in the phrase “having second thoughts”
35. second to none: better than anyone or anything else
36. second wind: restoration of easy breathing after physical exertion, or a renewal or energy or strength
37. seventh heaven: a state of bliss
38. sixth sense: a perceptiveness that cannot be achieved with the five physical senses
39. think twice: carefully consider
40. the third degree: intense questioning
41. third rail: something dangerous, like the electrified third rail of an electric railway system
42. third time’s the charm: one will succeed on the third try
43. Third World: the undeveloped world, first used to describe countries not aligned with the world’s democratic and communist nations during the Cold War
44–45. third/fifth wheel: a person thought to be unwelcome in the company of a pair or quartet of people; usually a reference to a single person with one or two couples
