Similarity and identity

To say that people or things are similar, we can use as or like, so/neither do I and similar structures.

You look just like your sister.
He fought like a tiger.
He fought as a tiger does.
She likes traveling. So do I.
She didn’t come. Neither did he.

To say that people or things are identical we use the same as.

Your eyes are the same color as mine.

To say that people or things are not similar, we can use the negative forms of the structures used for talking about similarity.

She doesn’t look like her sister.
He didn’t fight like a tiger.
She doesn’t like traveling. Neither do I.
She came. So did he.
Your eyes are not the same color as mine.

Note that we use neither do I after a negative statement. We use so do I after an affirmative statement.

To say that people or things are equal in a particular way, we use a structure like as…as.

She earns as much money as he does.
You are as tall as he is.
She is as beautiful as her sister (is).

In negative comparisons we can use not as…as or not so…as.

She does not earn as much as he does.
You are not so tall as he is.
She is not as beautiful as her sister (is).

Comparison using comparative adjectives and adverbs

To say that people or things are unequal in a particular way, we can use comparative adjectives or adverbs.

She is much taller than her husband.
She is more beautiful than her sister.

We can also talk about inequality by using less or least.

She is less beautiful than her sister.