极了【jí le】

极了 after an adjective pushes it to the top: "extremely", "incredibly". It's spoken and lively, and it works for good and bad alike.

After the adjective, without 很

Degree words like 很 and 非常 go before an adjective; 极了 goes after it. One degree is enough, so 很 drops.

• × 今天很热极了 → 今天热极了
• × 今天极了热 → 今天热极了

Feelings and 得

Verbs of feeling like 喜欢 and 高兴 take 极了 too. An object goes to the front, since nothing can follow 极了.

• × 我喜欢极了这首歌 → 这首歌我喜欢极了

After a verb and 得, it describes how something was done.

No negative

极了 doesn't follow 不. For "not at all", use 一点儿也不.

• × 这个菜不好吃极了 → 这个菜一点儿也不好吃

死了 after an adjective is the blunter, mostly negative version: 累死了, 热死了.