可 (kě) can be used to intensify an adjective, or to add emphasis to a verb. It is stronger than other modifiers, as 可 compares the speaker‘s expectations with the actual situation. The meaning of 可 is very reliant on context.

可 is generally used by Northern speakers and is informal, generally only used in spoken Chinese.

可 used to intensify an adjective
Basic Structure

可+adjective
Examples

In these examples, 可 is used a bit like 很, as it is used to intensify an adjective:

zhè zhǐ xiǎo ɡǒu kě táoqì le!
这 只 小 狗 可 淘气 了!
(The speaker never expected dogs to be this naughty) These dogs are so naughty!

wā,zhè ɡè tánɡcù lǐjǐ kě hǎochī le!
哇,这 个 糖醋 里脊 可 好吃 了!
(The speaker never dreamt that sweet and sour pork could taste this good) Wow! This sweet and sour pork is delicious!

可 used to emphasize a verb
Basic Structure

可+verb
Examples

In these examples 可 is used a bit like 真, and used to emphasize a verb:

nǐ kě lái le!
你 可 来 了!
(The speaker never expected it would take so long for you to get here)

nǐ kě bié hē tài duō jiǔ。
你 可 别 喝 太 多 酒。
(I'm not expecting you to drink a lot)

nǐ kě bié zǒu!
你 可 别 走!
(I'm blocking your way, almost pleading with you, as I believe you are going to leave)

huà kě bú nénɡ zhè yànɡ shuō。
话 可 不 能 这 样 说。
(What you said doesn't accord with my own beliefs)

In two of the sentences above, 可 is used with 别, and sounds a bit like "don't even think about..." in English.