1. to mark the boundaries or limits of something
2. to separate or distinguish clearly between different things

Examples

• The fence demarcates the property line between the two houses.
• A clear line demarcates the playing field from the spectator area.
• The treaty demarcates the border between the two countries.
• The river demarcates the northern boundary of the national park.
• This policy demarcates acceptable behavior from unacceptable conduct.
• The study demarcates three distinct phases of development.
• A stone wall demarcates the ancient cemetery grounds.