太…了【tài … le】

太 + adjective + 了 says something has gone past the acceptable point: "too". The 了 is part of the pattern and is not left out.

• × 这个太贵。 → 这个太贵了。

Also as an exclamation

With a positive adjective it stops meaning "too much" and becomes admiration.

With an adjective that is neither good nor bad, context decides: 太大了 can be a complaint or a compliment.

不太 for softening

bù不tài太 means "not very". It turns a negative into a polite understatement.

不太好 is a gentle way of saying something is bad.

不太 takes no 了 of its own

The 了 belongs to the affirmative pattern. A 了 after 不太 + adjective is the 了 of a changed situation, and the meaning shifts to "not so … any more".