| Certain number: Abbr. | 21 |
| Certain numbered hwy. | 21 |
| Certain numbers | 15 |
| Certain numbers in arithmetic | 29 |
| Certain numerals | 16 |
| Certain numerical prefix | 24 |
| Certain numero | 14 |
| Certain nun | 11 |
| Certain nursery rhyme intro | 27 |
| Certain nursery-men | 19 |
| Certain nuts | 12 |
| Certain nuts, for short | 23 |
| Certain NYC pro | 15 |
| Certain oar | 11 |
| Certain oarsmen | 15 |
| Certain Obama appointee | 23 |
| Certain object of art | 21 |
| Certain objector acronymically | 31 |
| Certain objet d'art | 23 |
| Certain occultist | 17 |
| Certain occupancy privileges | 28 |
| Certain occupation | 18 |
| Certain Oceanian, informally | 28 |
| Certain odor absorber | 21 |
| Certain of govt. agt. | 21 |
| Certain off-road excursion | 26 |
| Certain office machine output | 29 |
| Certain office worker | 21 |
| Certain officer | 15 |
| Certain official | 16 |
| Certain offshoot | 16 |
| Certain offspring | 17 |
| Certain Ohio baseballer | 23 |
| Certain Ohioans | 15 |
| Certain oil paintings | 21 |
| Certain oil producers | 21 |
| Certain oil wells | 17 |
| Certain ointments | 17 |
| Certain Oklahoma native | 23 |
| Certain old maid | 16 |
| Certain old TV accessory | 24 |
| Certain old-woman's home | 28 |
| Certain Oldsmobile | 18 |
| Certain olives | 14 |
| Certain Olympian | 16 |
| Certain Olympians | 17 |
| Certain Olympic athlete | 23 |
| Certain Olympic contender | 25 |
| Certain Olympic team letters | 28 |
| Certain one of a series of clones of a 1990s presidential contender? | 68 |
| Certain one, in Berlin | 22 |
| Certain one, to Louis I | 23 |
| Certain one-time Yugoslavian | 28 |
| Certain ones | 12 |
| Certain ones on the sidelines | 29 |
| Certain ones, in Brooklyn | 25 |
| Certain online request | 22 |
| Certain Ontarian | 16 |
| Certain OPEC minister | 21 |
| Certain open-air drinking establishment | 39 |
| Certain opening | 15 |
| Certain opening night attendee | 30 |
| Certain opening words | 21 |
| Certain opening-night attendee | 30 |
| Certain opera singer | 20 |
| Certain opera singers | 21 |
| Certain operating system | 24 |
| Certain operative | 17 |
| Certain operators | 17 |
| Certain optimist | 16 |
| Certain optimists | 17 |
| Certain oranges | 15 |
| Certain orbital points | 22 |
| Certain orchestra | 17 |
| Certain orchestra member | 24 |
| Certain ore | 11 |
| Certain ore content | 19 |
| Certain Oregon resident | 23 |
| Certain organ part | 18 |
| Certain organic compound | 24 |
| Certain organic compounds | 25 |
| Certain organizations | 21 |
| Certain organs | 14 |
| Certain orgs. | 13 |
| Certain Oriental rug maker | 26 |
| Certain oriental women | 22 |
| Certain ornamentations | 22 |
| Certain ornaments in architecture | 33 |
| Certain orthodox Jew | 20 |
| Certain orthoptera | 18 |
| Certain Oscar winners | 21 |
| Certain outbreak | 16 |
| Certain outdoor growing area | 28 |
| Certain outdoorsman | 19 |
| Certain outing | 14 |
| Certain overalls | 16 |
| Certain overimbiber | 19 |
| Certain overseas reporter | 25 |
| Certain overthrown leader | 25 |
| Certain ovines | 14 |