Through their guidance and love, they have changed me in many ways.

Is the above sentence grammatically correct?

Thanks!

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I wasn't sure if the comma should be there or not...

Yes. Your comma is correct. A fairly long prepositional phrase that begins a sentence is usually set off with a comma. Commas are used to clarify the sentence -- and this sentence is certainly easier to read with the comma.

Thank you!

:]

Yes, the sentence you provided is grammatically correct. It is a complete sentence, consisting of a subject "they" (referring to someone or a group of people) and a predicate "have changed me in many ways." It expresses how the guidance and love from "they" have had a transformative effect on the speaker.

To determine the grammatical correctness of a sentence, you can consider the following elements: subject (who or what the sentence is about), verb (action or state of being), and predicate (the part of the sentence containing the verb and providing more information about the subject). In this case, the subject is "they," the verb is "have changed," and the predicate is "me in many ways." These elements combine to form a grammatically correct sentence.