Therefore means “for that reason” or “as a result of what was just said.” It's a signpost word that connects a reason to its conclusion, showing your reader or listener how your logic flows.

When you write “I studied hard for the spelling test; therefore, I felt confident,” you're showing the direct connection between studying and feeling confident. The word signals: here comes the logical result of what I just told you.

Therefore appears frequently in mathematical proofs and scientific writing because it marks each step of reasoning. A mathematician might write: “The angles of a triangle always add up to 180 degrees; therefore, this angle must be 60 degrees.” Scientists use it to connect observations to conclusions: “The plant received no water for two weeks; therefore, it wilted.”

You'll also see therefore in formal speeches and careful arguments. It carries more weight than casual words like “so” or “that's why.” When someone says therefore, they're being deliberate about showing their reasoning, making their argument stronger and clearer.

The word works best when the connection is truly logical. If you write “It's Tuesday; therefore, I like pizza,” readers will notice something's wrong because there's no real connection between those ideas.