Idioms are phrases which cannot be understood simply by looking at the meaning of the individual words in the phrase.
Idiom:
head over heels
Meaning:
upside down, head first
Example:
The boy fell head over heels when his bicycle hit the wall.
List of common idioms, their meanings and examples of their usage in sentences
An expression in the usage of a language that is peculiar to itself either in having a meaning that cannot be derived from the conjoined meanings of its elements or in its grammatically atypical use of words.