Idioms
A group of words which have a different meaning when used together from the one they would have if you took the meaning of each word separately.
Idiom:
knit one's brow
Meaning:
to wrinkle one's brow by frowning
Example:
The teacher knit his brow and looked sternly at the child.
List of common idioms, their meanings and examples of their usage in sentences
The language peculiar to a people or to a district, community, or class