a complete sentence has at least a subject and a main verb to state (declare) a complete thought. short example: "she walks". a subject is the noun that is doing the main verb. the main verb is the verb that the subject is doing. in english and many other languages, the first word of a written sentence has a capital letter. at the end of the sentence there is a punctuation mark depending on whether it is a statement, a question, a command, a request or an exclamation.