A main clause is a group of words that contains a subject and a verb, and it expresses a complete thought. It can stand alone as a sentence. For example, in the sentence “The dog barks,” “The dog” is the subject, and “barks” is the verb, making it a main clause. Main clauses can also be part of larger sentences that include subordinate clauses. For instance, in the sentence “Although it was raining, the children played outside,” “the children played outside” is the main clause, while “Although it was raining” is a subordinate clause that cannot stand alone.