A bar (also called an overbar) is a horizontal line written above a mathematical symbol to give it some special meaning. If the bar is placed over a single symbol, as in (voiced " -bar"), it is sometimes called a macron.

What is the over symbol called?

What you seek is generally known as a “macron”, “overline”, “overscore”, or “overbar”. It exists at several Unicode code points; which one you want depends on whether you want a macron or an overline (the former being shorter), and whether or not you want a combining character.

What is the line above a word called?

Diacritical marks can be squiggles, lines, or dots, and they can hover above a letter or be attached to it. They're also known as diacritics or accents.