Заперечення з префіксом ne-

To say "not", Czech glues ne- onto the front of the verb and writes the two as one word. There is no helper verb like English "don't": "I don't understand" is just Nerozumím.

Because Czech stress always falls on the first syllable, adding ne- moves the stress onto it: RO-zu-mím, but NE-ro-zu-mím. Say it that way and you will sound Czech at once. The only irregular form is the one in the last row: the negative of je is není.

Two negatives do not cancel out

This is the rule English speakers break most. In standard English a sentence takes one negative: "Nobody came", "I never drink coffee". In Czech every negative word comes with a negative verb, and they reinforce each other:

*Nikdo je doma or *Nikdy piju kávu are simply wrong. If it helps, think of the Rolling Stones' "I can't get no satisfaction": what is slang in English is the grammar of standard Czech. You can stack as many as you like: Nikdo nikdy nic neví. - "Nobody ever knows anything."

The negative words come in pairs with their positive partners: někdo / nikdo (somebody / nobody), něco / nic (something / nothing), někde / nikde (somewhere / nowhere), někdy / nikdy (sometimes / never). And plain "no" is ne: Ne, děkuju.