Грамматика русского языка. Часть 8. Глагол. Глава 15. Отрицание (Продолжение). Russian Grammar. Part 8. The Verb. Unit 15. Negatives (Continued).

In Russian there are negative words which are used with infinitives, not with conjugated verbs (e.g. there is nothing for me to do). These negataves begin with the stressed syllable не.

(А) The key negative words used with infinitives (with very literal translations into English) are:

негде	not whеre	Негде стоять	There's nowhere to stand.
некуда	not to where	Некуда идти	There’s nowhere to go.
некто	not who	Некого спросить	There's no one to ask.
некогда	not when	Некогда отдыхать	There's no time to rest.
нечто	not what	Нечего есть	There’s nothing to eat.

The negatives нечто and некто decline like что and кто; if they are used with a preposition, then the preposition must follow the не part of the word:
Нечем писать.   There's nothing tо write with.
Не на что жаловаться.   There's nothing to complain about.

(В) If you want to indicate who has nothing to eat, nowhere to rest etc., then you must use the dative case of that person:
Вам не на что жаловаться.   You've got nothing to complain about.
Мне нечем писать.   I've got nothing to write with.

(С) These negative and infinitive phrases can be put into a past or future context by using the past and future tenses of быть:
Мне нечем было писать.   I had nothing to write with.
Вам не на что будет жаловаться.   You will have nothing to complain about.

(D) Нечего can be used to mean there's no point. Не за что can be used to mean don't mention it, you're welcome.