border

The border of a country is the edge of the country: the place where that country touches another country.

Example: You can't cross the border without identification papers.

The border of a shape or of a picture or of part of a picture is the edge of it.

Example: She drew three pink hearts with red borders at the top of the picture.

If something is bordered with or in something, that goes all around it.

Example: The newspaper notice was bordered in black.

If one place borders on another, they are side by side.

Example: The Sea of Japan is bordered by Japan, North Korea, Russia and South Korea.