Comma splicing ✗ She has an advanced degree in biochemistry, therefore, she’s the best candidate. ✓ She has an advanced degree in biochemistry, and therefore is the best candidate. ✓ She has an advanced degree in biochemistry; therefore, she’s the best candidate. ✓ She has an advanced degree in biochemistry. Therefore, she’s the best candidate. Omitting a semicolon ✗ The two lines intersect therefore, they are not parallel. ✓ The two lines intersect; therefore, they are not parallel. Mistaking it for “therefor” (which means “for or in return for that”) ✗ The metal bracelet was made using mid-century welding techniques; therefor, it is a legitimate antique. ✓ The metal bracelet was made using mid-century welding techniques; therefore, it is a legitimate antique. Using it in informal settings (this is not against the rules, but “so” sounds more natural) ✗ The trip was cancelled and, therefore, I visited my aunt instead. ✓ The trip was cancelled, so I visited my aunt instead.