Use 'as + [adjective/adverb] + as' to compare two things.
- You are as tall as Tom. (= You and Tom are the same height)
- You run as fast as Tom.
Use 'just' to emphasize that the two nouns are exactly the same:
- My room is just as big as your room! (= My room is exactly the size of yours)
To form a negative sentence use 'not as…as'.
- You are not as tall as Tom. (= You are shorter than Tom)
Interrogative 'as... as...'
Remember: To form questions with the verb 'be', switch the order of the subject and 'be'. The same applies to questions with 'as... as...' : 'be' + subject + as... as....
- You are as tall as Tom. → Are you as tall as Tom?