How can I express that X is as big/small/fast/... as Y?


I would like to know how to express that something is equal in some aspect to
another thing (or person, if that makes a difference), as you would express in
English by saying:

X is as (adjective) as Y

for example: This car is as fast as that car.

It would also be interesting for me to learn how to say:

"is not as (adjective) as" "is nearly as (adj) as" "can/might/will be as (adj)
as" "want to be as (adj) as"




In addition to `くらい／ぐらい` as @rintuan mentioned, `ほど` (meaning "extent" or
"limit") is your friend:

> ### X is not as (adjective) as Y → ほど〜ない
>
>   * あの少年はお兄さん **ほど** 背が **高くない** → That boy is not as tall as his older
> brother.
>   * 生物学は物理学 **ほど** 面白く **ない** → Biology is not as interesting as physics.
>

>
> ### Other comparisons: "to the extent of 〜"
>
>   * 今日はセーターを着るほど寒い → Today is cold enough to (need to) wear a sweater;
> "Today is cold to the extent of wearing a sweater"
>

Some other alternatives:

> ### Two things being nearly equal in some aspect
>
>   * この車とあの車と、速さはだいたい同じ → This car is about as fast as that car; "As for this
> car and that car, their speeds are about the same"
>   * ねこくらいの大きさのネズミ → A rat (about) as big as a cat
>

