Is there a comma before therefore?

Yes, there is usually a comma before therefore when it is used as a conjunctive adverb. A conjunctive adverb is a word or phrase that connects two clauses or sentences and also expresses a relationship between them. Therefore is a conjunctive adverb that indicates a logical conclusion or consequence. When therefore is used in this way, it is preceded by a comma.

For example:

- The sky is clear, therefore we can go for a walk.

- She studied hard, therefore she got good grades.

- He did not study, therefore he failed the test.

However, if therefore is used as an adverb within a sentence, it does not require a comma.

For example:

- Therefore, we can conclude that the hypothesis is correct.

- The experiment failed; therefore, we need to start over.

- He arrived therefore late for the meeting.