Hidden (Implied) Subjects. In the case of a command - that is, when someone is telling you to do something - there won't be any clear subject in the sentence. Instead, the subject is implied - the subject is you!
When looking for the subject in a sentence, look for the verb first. Remember that a verb is a word that either helps a subject perform an action (ran, drank, fights, swims) or shows a state of being (is, was, are, were) that connects the subject to the action.
A simple subject is just the subject without any of its modifiers (adjectives, adverbs - that is, any explanatory details).
Sentences can also have more than one verb, more than one subject, or multiple pairs of subjects and verbs.
Conjunctions can join multiple subjects or verbs as well as independent and dependent clauses.
When you see a personal pronoun - 'I,' 'you,' 'he,' 'she,' 'it,' 'we,' and 'they' - a verb will follow. One exception to this rule is when the pronoun refers to the earlier subject.
In a passive sentence, the subject does not 'do' the action; the action instead happens to the subject.
Find examples and learn more on How to Identify the Subject of a Sentence at Study.com.