The Many Meanings of 厉害

厉害lìhài is a really cool and fun multipurpose word.  This grammar section will be pretty short, since it's more of a "how neat is that?" over how the word 厉害lìhài is super 厉害lìhài.

厉害lìhài at it's root means ferocious, violent, terrible, etc specifically when talking about animals.  However, today it is most commonly used to express any of these words: "amazing, awesome, impressive, great, fantastic, powerful!".  It is a very emphatic word and serves well as a complement.

Nǐ de zhōngwén hěn lìhài! Nǐ shì zěnme xué de? 你的中文很厉害！你是怎么学的？ Your Chinese is amazing! How did you learn？

Zuótiān de yóuyǒng bǐsài, měiguó duì zuì lìhài. 昨天的游泳比赛，美国队最厉害。 In yesterday's swimming competition, America was the most impressive.

Wa, zhège jiǎozi shì nǐ bāo de ma? Zhēn de hěn lìhài! 哇，这个饺子是你包的吗？真的很厉害！ Whoa! This dumpling was wrapped by you? It's fantastic!

厉害lìhài is still used for it's original context, though way less frequently.  Sometimes we will add 厉害lìhài on to awful circumstances to emphasize the degree of seriousness. In these cases, it is most often translated as, "terribly, horribly, etc".

Tā māmā bìng dé hěn lìhài.
他妈妈病得很厉害。
Her mom is terribly sick.