| One-quadrillionth: Comb. form | 29 |
| One-quarter of "Whose woods these are I think I know" | 63 |
| One-quarter of a mourning lacrosse team? | 40 |
| One-quarter of an H, in Morse code | 34 |
| One-quarter of doce | 19 |
| One-quarter of quadri- | 22 |
| One-quarter of quarante | 23 |
| One-quarter of tetra- | 21 |
| One-quarter of zero? | 20 |
| One-quintillionth: Prefix | 25 |
| One-room abode | 14 |
| One-room apartment | 18 |
| One-room dwelling | 17 |
| One-room heater | 15 |
| One-room home | 13 |
| One-room house, typically | 25 |
| One-room pad | 12 |
| One-room schoolhouse features | 29 |
| One-room schoolhouse figure | 27 |
| One-room schoolhouse heater | 27 |
| One-round loser to Muhammad | 27 |
| One-run homers | 14 |
| One-scene role | 14 |
| One-seat carriages | 18 |
| One-seated vehicle | 18 |
| One-seater race | 15 |
| One-seeded fruit | 16 |
| One-seeded fruit, botanically | 29 |
| One-seeded fruit: Var. | 22 |
| One-seeded fruits | 17 |
| One-seeded fruits: Var. | 23 |
| One-seeded, winged fruit | 24 |
| One-seventh of a rainbow | 24 |
| One-seventh of a semana | 23 |
| One-seventh of una semana | 25 |
| One-sharp musical key | 21 |
| One-sided | 9 |
| One-sided ballgame | 18 |
| One-sided battle | 16 |
| One-sided contest | 17 |
| One-sided contests | 18 |
| One-sided court score | 21 |
| One-sided figure formed with a twist | 36 |
| One-sided game | 14 |
| One-sided melee | 15 |
| One-sided person | 16 |
| One-sided plurality | 19 |
| One-sided result | 16 |
| One-sided score | 15 |
| One-sided series | 16 |
| One-sided tilts | 15 |
| One-sided victory | 17 |
| One-sided victory for Baltimore | 31 |
| One-sided win | 13 |
| One-sided wins | 14 |
| One-sidedness | 13 |
| One-sixteenth of a cup (Abbr.) | 30 |
| One-sixteenth of a cup: Abbr. | 29 |
| One-sixth drachma | 17 |
| One-sixth of a drachma | 22 |
| One-sixth of a fl. oz. | 22 |
| One-sixth of a shilling | 23 |
| One-sixth of an inch | 20 |
| One-sixth of an inch, in printing | 33 |
| One-sixth of dieciocho | 22 |
| One-sixth of MD | 15 |
| One-sixtieth of MMMCXX | 22 |
| One-spot | 8 |
| One-spot card | 13 |
| One-spot cards | 14 |
| One-spots | 9 |
| One-stanza poem | 15 |
| One-star | 8 |
| One-star hotel attraction | 25 |
| One-star men: Abbr. | 19 |
| One-star officer | 16 |
| One-star people | 15 |
| One-star ratings | 16 |
| One-star write-up | 17 |
| One-stop font shop? | 19 |
| One-story home | 14 |
| One-story houses | 16 |
| One-story, two-story house | 26 |
| One-stripe G.I.'s | 21 |
| One-stripe GI | 13 |
| One-stripe GIs | 14 |
| One-stripe soldiers: Abbr. | 26 |
| One-striper, briefly | 20 |
| One-striper, for short | 22 |
| One-striper: Abbr. | 18 |
| One-stripers, for short | 23 |
| One-stroke score | 16 |
| One-syllable Greek letter | 25 |
| One-syllable laugh | 18 |
| One-tenth | 9 |
| One-tenth ephah | 15 |
| One-tenth levy | 14 |
| One-tenth of a G | 16 |
| One-tenth of a microjoule | 25 |
| One-tenth of a millennium (abbr.) | 33 |