| Subject | English | Russian |
| gen. | I don't know for certain | я точно не знаю |
| gen. | I don't know for certain | я не уверен |
| inf. | I know it for certain | мне это доподлинно известно |
| gen. | know for certain | точно знать (With the captain’s report everything came together — secret bases, government cover-ups, global warfare, ancient aliens, pyramid power — to create the story of the Black Pyramid. The story that Campbell, if he followed any of the internet lore, surely planned his summer vacation around. No one knows for certain if Campbell believed any of this.  anomalien.com ART Vancouver) |
| gen. | know for certain | знать наверняка (With the captain’s report everything came together — secret bases, government cover-ups, global warfare, ancient aliens, pyramid power — to create the story of the Black Pyramid. The story that Campbell, if he followed any of the internet lore, surely planned his summer vacation around. No one knows for certain if Campbell believed any of this. anomalien.com ART Vancouver) |
| saying. | no one can know for certain | Либо дождь, либо снег, либо будет, либо нет (Alex Lilo) |
| saying. | no one can know for certain | одному Богу известно (Alex Lilo) |
| saying. | no one can know for certain | Бабушка гадала, надвое сказала (Alex Lilo) |
| gen. | not to know for certain | не знать наверняка |
| saying. | one can't know for certain which way the cat would jump | одному Богу известно |
| saying. | one can't know for certain which way the cat would jump | Либо дождь, либо снег, либо будет, либо нет |
| saying. | one can't know for certain which way the cat would jump | Бабушка гадала, надвое сказала |
| scient. | we don't know for certain | мы точно не знаем |
