怪不得【guàibude】

怪不得 reacts to new information that explains something you'd noticed: "no wonder", "that explains it". It's spoken and lively, and very often a whole reply on its own.

The reason can come first, or after 怪不得 with 原来.

It means the same as 难怪. 难怪 is a touch more neutral and turns up in writing; 怪不得 belongs to conversation.

Where it goes

怪不得 opens its clause, before the subject.

• × 他怪不得没来 → 怪不得他没来

"It's not their fault"

Followed directly by a person, 怪不得 is a verb: "you can't blame them". 怪 on its own means "to blame".