A lord is a person who holds power, authority, or high social rank. In medieval times, a lord owned land and had authority over the people who lived and worked on it. Knights, vassals, and peasants would pledge loyalty to their lord, who in turn protected them and administered justice. The lord of a castle controlled the surrounding countryside, collected taxes, and maintained order.

In British society, “Lord” is still used as a title of nobility, like Lord Byron or Lord Nelson. Members of Britain's House of Lords carry this title. The word can also show respect or authority more generally: a landlord owns property that others rent, and in some religions, people refer to God as “the Lord.”

When someone acts like they're superior to everyone else, we might say they're lording it over others, meaning they're showing off their power or status in an annoying way. If your older brother got to stay up late and kept reminding you about it, he'd be lording it over you.

The phrase lord of the manor refers to someone who acts like they own a place, whether they actually do or not. And when people say “Good Lord!” they're expressing surprise or dismay, using an old-fashioned way of speaking.