Hence means “for this reason” or “as a result of this.” When you write or speak, hence connects a cause to its effect, showing that what comes next is a logical consequence of what came before.

If you say, “I studied hard for the test, hence my good grade,” you're explaining that the good grade happened because you studied. If a scientist writes, “The experiment failed three times; hence, we redesigned our approach,” the word hence shows that the failures led directly to the new design.

Hence sounds formal and appears most often in careful writing: essays, scientific papers, or speeches. In casual conversation, people usually say “so” instead. You might tell a friend, “I'm tired, so I'm going to bed early,” but you'd write in an essay, “The data were incomplete; hence, the need for further research.”

The word also has an old-fashioned meaning related to “from here” or “from now,” which you might encounter in older books. When Shakespeare wrote “Get thee hence,” he meant “Go away from here.” When someone says “ten years hence,” they mean ten years from now. But in modern usage, hence almost always means “for this reason.”