b. conjunction introducing clauses of manner, comparison or comment.
    e.g. manner: She cooks rabbit exactly as her mother did.
           comparison: They hunted him as a tiger stalks (to stalk=besluipen) his prey.
           comment: As you all know, England is an island.

As if
conjunction introducing clauses of manner and comparison that are hypothetical, i.e. that imply negative bias (=neiging)

It was as if we were on the sun. (but we weren't, of course)
He fought as if his life was in danger. (very hard, unusually hard)

Such as
Is used before a list of examples. In less formal speech it can be replaced by "like".

Countries in the north of Europe, such as Finland, Norway, Sweden,...

Like
is a preposition used to express comparison or manner. It is not a conjunction and cannot be followed by a finite verb. (compare "as" meaning b)

e.g. That's just like him.

You will probably have noticed that some native speakers use "like" as a conjunction instead of "as". If your aim is educated English you should not imitate them.

So
is an adverb of degree. The word always has stress.

e.g. I have never felt so free!

Some students have a preference for "that", a habit they have picked up from popular songs and films. Again, this is not considered to be acceptable speech by speakers of correct English.
 
 
 

Jenn Van Loock
English teacher at KHK teacher training college Vorselaar, Belgium.