Negation: не, нет and the obligatory double negative
не sits directly before the word it negates, нет takes the genitive and is present-tense only, and double negation is compulsory.
Не is the general negative particle and it goes immediately before whatever it negates, most often the verb: Я не чита́ю, Он не зна́ет. It can also negate an adjective or an adverb — не больша́я ко́мната, не здесь — and a noun predicate, where it also removes the dash: Он не врач. Nothing else in the sentence moves. If you know Italian non, the transfer is direct and completely positive.
Нет is a separate word, not не plus есть, and it does a different job. It is the negative of 'there is' and of possession: У меня́ нет вре́мени (I don't have time), В ко́мнате нет стола́ (there is no table in the room). The noun that follows it goes into the Genitive case. Critically, нет is a present-tense form only. In the past you use не бы́ло plus the Genitive, and in the future не бу́дет plus the Genitive: Вчера́ у меня́ не бы́ло вре́мени. Saying *Вчера у меня нет времени is one of the commonest beginner errors there is.
Double negation is not a mistake in Russian, it is the rule. Every negative element in the clause must be negative. Я ничего́ не зна́ю — literally 'I nothing not know'. Никто́ никогда́ мне не звони́л — 'nobody never to me not rang'. There is no equivalent of English 'any-' words; you keep не on the verb and add the negative pronoun on top of it. This takes deliberate unlearning for an English speaker and it feels wrong for weeks.
The pair не and ни needs one clear distinction. Ни is the unstressed element inside the negative pronouns and adverbs — никто́, ничего́, никогда́, нигде́, никуда́ — and in the emphatic construction ни … ни meaning 'neither … nor': Ни чай, ни ко́фе — спаси́бо. Не is stressed in the two forms that appear when there is no verb to attach to: не́кого and не́чего, meaning 'there is nobody to' and 'there is nothing to'. Не́кого спроси́ть — there is nobody to ask. Finally, in careful written Russian a negated direct object often shifts into the Genitive (Я не чита́л э́той кни́ги); the Accusative is always acceptable, so this is a refinement, not a rule you must obey at this level.
Examples
- Я не понима́ю. I don't understand. Listen in Russian: Slow in Russian: Я не понима́ю.
- У меня́ нет вре́мени. I don't have time. — нет + genitive Listen in Russian: Slow in Russian: У меня́ нет вре́мени.
- Вчера́ у меня́ не бы́ло вре́мени. Yesterday I didn't have time. — the past uses не было, never нет Listen in Russian: Slow in Russian: Вчера́ у меня́ не бы́ло вре́мени.
- Я ничего́ не зна́ю. I don't know anything. — double negation is obligatory Listen in Russian: Slow in Russian: Я ничего́ не зна́ю.
- Никто́ не звони́л. Nobody rang. Listen in Russian: Slow in Russian: Никто́ не звони́л.
- Он не врач, он инжене́р. He is not a doctor, he is an engineer. — не before a noun, and no dash Listen in Russian: Slow in Russian: Он не врач, он инжене́р.