Two group B determiners can be put together if the combination makes sense.
- We meet every few days.
- I have seen all seven films directed by him.
When a group B determiner is directly used before a noun, we do not use of.
- Have you got any rice? (NOT Have you got any of rice?)
- Few children came. (NOT Few of children came.)
- Most people like babies. (NOT Most of people like babies)
But if we have to put a group B determiner before a noun which has a group A determiner (articles, possessives, demonstratives) we use of.
Compare:
- Few children (Group B determiner + noun)
- Few of the children (Group B determiner + of + group A determiner + noun)
- Each boy
- Each of the boys
- Neither color
- Neither of the colors
- Most shops
- Most of the shops
In a few cases of can be used directly before a noun even if there is no group A determiner. This, for example, happens with proper nouns such as place names.
Most of Wales was under water.
The determiners no and every cannot be used before of. Instead we use none and every one.
Compare:
- No child
- None of the children
- Every boy
- Every one of the boys
We can use all, both and half without of before a noun with a group A determiner.
- All my friends OR All of my friends
- Both my parents OR Both of my parents
- Half his income OR Half of his income
Of cannot be left out before a pronoun.
- All of us (NOT All us)
The determiners each, every, either and neither are followed by singular nouns. But when these determiners are followed by of, the nouns should be plural in number.
Compare:
- Each boy
- Each of the boys (NOT Each of the boy)
- Neither girl
- Neither of the girls
- Every girl
- Every one of the girls