Subject/verb agreement is necessary in order to form a grammatical sentence. A subject, such as ‘the frog’ or ‘the frogs’ must each have an action that agrees with it (singular or plural). Singular subjects involve only one noun (person, place or thing) or pronoun (modifier of a noun, such as I, you, he, she, it etc.). Plural subjects, such as ‘the frogs,’ involve more than one noun or pronoun, such as we, they, etc. The verbs that go in the sentence following these subjects must agree.
Incorrect: The frog jump very high in the air and his long tongue go over his head as he smile for the camera.
Correct: The frog jumps very high in the air and his long tongue goes over his head as he smiles for the camera.
A subject is the part of the sentence that tells who or what is causing the action in the sentence. For example: ‘The very active frog enjoys jumping up in the air to get attention from those who watch him.’ In this sentence, the first part of the sentence is the subject (The very active frog). The subject does not always appear at the beginning of the sentence, however. Sometimes the subject is placed at or near the end of the sentence. For example: After jumping very high into the air, the frog was exhausted. In this case, ‘the frog’ is the subject and comes near the end of the sentence. In order to determine the subject of the sentence, you must figure out who or what is doing the action and not simply rely on the location of the word in the sentence.
A verb is an action word. It is something that the subject does and creates the action in the sentence. For example: ‘The frog flew into the air as he tried to catch the flies.’ In this case, the verbs are the words ‘flew’ and ‘catch.’ Verbs must always agree with the subject or subjects of a sentence.
Incorrect: The frog catch flies with his tongue as he leap into the air above the pond.
Correct: The frog catches flies with his tongue as he leaps into the air above the pond.