In the sentence ‘The cat sat on the mat,’ what is the subject?

In the sentence 'The cat sat on the mat,' the subject is 'cat'. In English, the subject of a sentence indicates who or what performs the action in the verb. Here, 'cat' is the noun performing the action 'sat'. 'The', an article, precedes the noun to specify it, while 'sat' is the verb performing the action, and 'mat' is part of the prepositional phrase 'on the mat'. Identifying the subject helps in understanding sentence structure and meaning.