Simple Definition:

Sanction is an official action taken by a person, organization, or government to punish or restrict someone or something (such as a country) that has behaved in a way that is considered unacceptable. It can involve imposing penalties, restrictions, or limitations.

Examples:

• The United Nations imposed economic sanctions on North Korea (they stopped trading and doing business with them) to discourage its nuclear weapons program.
• The school administration issued sanctions against the student (they might have suspended the student or given them a punishment) for cheating on the exam.

Very Simple Definition:

A sanction means a punishment or restriction on someone or something for doing something wrong.

Examples:

• Often when a country doesn’t agree with another country, they stop trading with it as a sanction.
• The government might use punishment such as extra taxes as a sanction against companies that destroy the environment.