Each vs Every.

‘Each’ and ‘every’ are determiners, words that are ‘used with singular nouns to indicate quantity’. There are differences between the two that are important to grasp for usage, though.

1. ‘Each’ is used when there are two objects; here ‘every’ is not used. For example,

• - He wore multiple bracelets on each hand (note: singular noun).
• - There were two of them. They each carried backpacks, and eachbackpack (note: singular noun) contained invaluable souvenirs.

In case there are more than two objects, either of the two may be used.

• - He wanted each/every item on the catalogue.
• - There is a bathroom in each/every room.

2. ‘Each’ can be used as a pronoun, but ‘every’ cannot. Note the difference between the following sentences:

• - The students were waiting for the question sheets to be handed out. Each was in a state of great nervousness.
• - The students were waiting for the question sheets to be handed out. Every student/one of them was in a state of great nervousness.

Clearly, ‘each’ replaces the noun ‘student’. ‘Every’ does not; it requires to be followed by the noun, or by ‘one of them’.

3. With adverbs (practically, nearly, almost, etc), only ‘every’ is used. In the following sentences, ‘every’ cannot be replaced by ‘each’:

• - She knew practically every detail of his daily routine.
• - Nearly every fruit on the cart was spoilt.

4. ‘Every’ is used to refer to repeated, regular events, as in the following cases:

• - We meet every so often
• - I get a health check-up done every six months.
• - I had to take a water break after every other set.

In the above examples and any similar instances, ‘each’ cannot be used.

Take from: http://www.englishleap.com/common-mistakes/each-every