| Subject | English | Russian |
| gen. | not to know the first thing about... | не понимать ни бельмеса о... |
| gen. | not to know the first thing about... | не знать ни бельмеса о... |
| gen. | not to know the first thing about something | ничего не знать о (Mongolian_spy) |
| amer. | not to know the first thing about something | ничего не шарить в чём-либо (You don't know the first thing about being rich Taras) |
| amer. | not to know the first thing about something | ничего не смыслить в чем-либо (Taras) |
| amer. | not to know the first thing about something | ничего не понимать в чем-либо (Taras) |
| gen. | not to know the first thing about something | не иметь понятия о (Mongolian_spy) |
| gen. | not to know the first thing about something | совершенно не разбираться (в чём-либо – If you say that you do not know the first thing about something, you are emphasizing that you know absolutely nothing about it. • You don't know the first thing about farming. Anglophile) |