1. a line that marks the limits of an area; a dividing line
2. a limit of what is acceptable or appropriate in behavior or relationships

Examples

• The fence marks the boundary between our property and theirs.
• The river forms a natural boundary between the two countries.
• She crossed the boundary line during the tennis match.
• It’s important to set clear boundaries with your children.
• He violated professional boundaries by dating a client.
• The boundary between work and personal life can be difficult to maintain.
• Respect other people’s boundaries and personal space.