可【kě】

可 before an adjective means "really, so", with feeling behind it. It is spoken, and the sentence usually closes with 了 or 呢.

Without 了 or 呢, 这儿可热 sounds cut off.

Warnings: 可别, 可要, 可不能

Before 别, 要 or 不能, 可 turns a request into a firm reminder: "make sure you…", "whatever you do, don't…".

Denying firmly

可不 and 可没 make a denial sharper: "it's certainly not", "I definitely didn't".

"Finally"

可 + verb + 了 greets something you've been waiting for.

Where it goes wrong

可 is the degree word, so 很 or 非常 can't join it.

• × 今天可很热 → 今天可热了

可 alone can also be short for 可是, "but", at the start of a clause. That 可 joins clauses; the emphatic 可 sits inside one.