Confidential means private and meant to be kept secret. When information is confidential, it's shared only with specific people who need to know it, and they're trusted not to tell anyone else.

A doctor keeps your medical records confidential, meaning they won't discuss your health with your neighbors or post about it online. When a teacher marks an email “confidential,” she's signaling that the contents shouldn't be shared around the school. Companies keep their business plans confidential so competitors can't copy their ideas.

When someone shares something confidential with you, they're trusting you to keep it private. Breaking that trust by revealing confidential information can seriously damage relationships and can even lead to legal trouble.

At school, you might hear the word in phrases like “confidential evaluation” or “kept in confidence.” If a friend tells you something in confidence, they're asking you to keep it between the two of you.