A two-member sentence has two members – a subject and a predicate. For example:
In its turn a two-member sentence may be complete or incomplete. It is complete when it has a subject and a predicate. It is incomplete when one of the principal parts or both of them are missing but can be easily understood from the context. Such sentences are called elliptical and are commonly used in colloquial speech. Ellipsis refers only to the structural elements of the sentence, not the informational ones. This means that those words can be omitted, because they have only grammatical, structural relevance, and do not carry any new relevant information. There are several types of elliptical sentences.
1. Sentences without a word-form in the subject position.
Looks like rain. Don’t know anything about it.
2. Sentences without word-forms in the subject position and part of the predicate position. In such cases the omitted part of the predicate may be either a) an auxiliary verb or b) a link verb.
a) Going home soon? See what I mean? Heard nothing about him lately.
b) Not bad. Free this evening?
3. Sentences without a word-form only in part of the predicate position, which may be an auxiliary or a link verb. For example:
You seen them? Everything fixed? You sure? All settled.
4. Sentences without word-forms both in the subject and the predicate position. Such ellipses occur in various responses.
What time does Dave come for lunch? - One o’clock.
What were you thinking about? - You.
5. Sentences without a word-form in the predicate position. Such ellipses occur only in replies to questions.
Who lives there? - Jack.
What’s happened? - Nothing.
A two-member sentence may be unextendedor extended.
Anunextended sentence contains two main positions of the basic pattern, that of the subject and the predicate. For example:
Mary laughed. Mary is happy.
An extended sentence may contain variousoptional elements (including attributes, certain kinds of prepositional objects and adverbial modifiers). For example,
John ran quickly to me. Mary laughed heartily at the joke.
Obligatory extending elements are those which complete the meaning of other words, usually verbs, or pronouns, which without them make no or little sense. Therefore obligatory elements are called complements.
John learned French. (the meaning of “learned” is incomplete without the object “French”)
John lives in London. (the meaning of “lives” is incomplete without an adverbial of place)