The word 'therefore' can be used as an adverb.
When used in this capacity, it is most commonly used to express a conclusion. In other words, it is often used to indicate the natural consequence of something that has just been expressed or stated. It can also be used to describe something that logically follows from what was previously expressed.
1. The numbers certainly added up, and therefore the calculations were correct.
2. The meeting came to a close, and therefore everyone agreed to the plan.
3. The issue was complex, and therefore resolution was difficult to achieve.
When used as an adverb, 'therefore' is typically preceded by either a clause or a semi-colon. It can usually be found between two clauses in a sentence that either provide a logical conclusion or inference stemming from the first clause or express a conclusion. Additionally, 'therefore' should typically be followed by a verb phrase.