Quote Originally Posted by Mr Smith View Post
В магазине ничего нет - There is nothing in the shop. or There is not anything in the shop.
В магазине нечего нет - not a valid sentence
The words with ни- are true negations (similar to the ones with no- in English, compare: nothing, nobody, nowhere).
In all those words the prefix "ни-" is unstressed (the stress falls on the root): никто, ничто, никакой, нисколько, нигде, никуда, ниоткуда, никак, никогда ...

Note that Russian uses the so-called "double negation" - the verb should also be negated if the sentence contains one of the listed above:

Этого никто не знает. No one knows it.
Ничто мне не поможет. Nothing will help me.
Я не читаю никаких книг. I read no books (no kind of them).
Я не потратил нисколько денег. I spent no money (zero amount).
Я нигде не видел такого красивого заката. I saw such a beautiful sunset nowhere.
etc. etc.

And if there are multiple pronouns, each one is negated:
Я никогда никому ничего не скажу. - I will never say anything to anyone. Literally: "I will not never say nothing to nobody".