A high religious title among Shia Muslims, used mainly in Iran and Iraq. An ayatollah is a senior scholar of Islamic law — someone who has studied for many years and is qualified to give rulings that other believers may follow. There are many ayatollahs; a very small number rise higher and are called Grand Ayatollah.

In English news, the word is most often attached to one man: Ayatollah Khomeini, who led the 1979 Iranian revolution, and then Ayatollah Khamenei after him. Because Iran's system gives its top cleric political power too, English speakers hear 'the ayatollahs' and think of the government, not just of religion — 'the ayatollahs closed the border'. That is a loose, journalistic use, and it flattens a religious rank into a political label.

There is also a mocking use, applied to anyone who lays down the law in a strict, unarguable way: 'the ayatollahs of health food', 'a grammar ayatollah'. It means a person who treats their opinion as sacred. This is informal and clearly unkind, and it will offend Muslim listeners, so it is safest to understand it and not use it.

Capitalise it before a name (Ayatollah Khomeini), lower case for the general noun (he became an ayatollah).