An idiom is defined as - a group of words whose meaning is different from the meanings of the individual words.
Idiom:
make hay while the sun shines
Meaning:
to do something at the right time, to take advantage of an opportunity
Example:
We will make hay while the sun shines and paint the house while the weather is good.
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.