Some languages, such as Spanish and Japanese, do not require a subject in every sentence. Every English sentence, however, needs a subject. An exception is commands, in which the subject you is understood but not present:
it as subject
The word it is used as the subject of a sentence in certain situations:
Subject following verb
In most English sentences, the subject appears before the verb. Some sentences, however, are inverted: The subject comes after the verb. In these sentences, a placeholder called an expletive (there or it) often comes before the verb.
Notice that the verb agrees with the subject that follows it: apple is, sects are.
Some inverted sentences have an infinitive (to work) or a noun clause (that she is intelligent) as the subject. In such sentences, the placeholder it is needed to open the sentence. It is followed by a linking verb (is, was, seems, and so on), an adjective, and then the subject.
here and there
The words here and there are not used as subjects. When they mean “in this place” (here) or “in that place” (there), they are adverbs—not nouns—and can’t be used as the subject of a sentence.
Exercises:
Omissions and repetitions 1
Omissions and repetitions 2
Sentence structure 1
Sentence structure 2
Related topics:
Linking verbs and subject complements
Verbal phrases
Noun clauses