as

1

Countries as China and India have large populations.
Countries such as China and India have large populations.
Countries like China and India have large populations.

We use such as or like, not as, to introduce examples.

2

I felt as I was suddenly very old.
I felt as if I was suddenly very old.

We use as if or as though, not as, to say how a situation seems or feels.

3

This car is not as the cars I used to drive when I was young.
This car is not like the cars I used to drive when I was young.

We normally use like, not as, before a noun when we mean ‘similar to’: ‘You are just like your mother.’

We use as + adjective/adverb + as in comparisons: ‘He is as tall as his brother.’ In negative comparisons, we use not as + adjective/adverb + as: ‘These shoes aren’t as expensive as mine.’

We also use as after the same: ‘It is the same colour as mine.’