An idiom is defined as - a group of words in a fixed order that has a particular meaning that is different from the meanings of each word on its own.
Idiom:
run a tight ship
Meaning:
to run an organization or one's life or a ship in an orderly and disciplined manner
Example:
My friend runs a tight ship and makes few mistakes in his life.
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.