Q.    What is the difference between 'most', 'most of' and 'almost?'  Why can you say 'most people', 'most of the people', but not 'almost people?' (Keiko, Japan)

Good question Keiko. I think many students have problems with this area of grammar, but there is a simple explanation. Let’s take a look at it and hopefully all will become clear!

Why don’t we start with some terminology? Most and most of work like adjectives, so they usually come before nouns (as in most people and most of the people). However, almost has the same meaning as nearly and is used as an adverb. For this reason, it is incorrect to say almost people just as it is also wrong to say nearly people!  

Take a look at this correct example:
The boy nearly passed the exam.   and  The boy almost passed the exam.
Here passed is a verb so the words nearly or almost are used to describe the verb.

However, many students get confused because most and almost all look similar. Consider the following example:
Almost all teenagers like pop music.   and   Most teenagers like pop music.
Here you can say most teenagers or almost all teenagers and here the meaning is the same (and is followed by a noun!).

So, what is the difference between most/almost all and most of/almost all of?

Look at these examples:
Most/Almost all teenagers enjoy spending time with their friends.
Here, we are talking in a general sense - we don’t know which teenagers we are talking about.

Compare that sentence with this one:
Most of the teenagers/Almost all of the teenagers enjoyed the party.
Here, we are talking about a particular group of teenagers. 

So, you just need to think about if you are talking in a general sense or referring to a particular group.  

Try to do these examples (remember that there are two possible answers!):

(1)   We’ve eaten ……………………./………………………. we bought.  There’s very little left! (most/almost all/food)

(2)    ………………./………………… is bought at supermarkets. (most/almost all/food)