What are often used to define the edge or boundary of something?
unity
lines
texture
rhythm

The answer is "Lines."

Explanation:

A "line" is considered one of the fundamental elements when it comes to "art." It comes in different forms such as "straight lines," "curved lines," "diagonal lines," "spiral lines," etc.

When it comes to certain situations such as "creating shapes," the lines are used to define the edge or boundary of something. As a boundary, the line functions to circumscribe the shape (such as a circle).

Thus, this explains the answer.

melody. a series of single tones which add up to a recognizable whole is called a what kind of layers of sound are heard melody or harmony. how many layers

nope becasue a mosque is a place where muslims pray to god, but the taj mahal was built by (forgive me) someone for his wife. i dont think anyone prays there. also a mosque is for muslims but indians are hindi.