A sentence is a unit of speech whose grammatical structure conforms to the laws of the language and which serves as the chief means of conveying a thought.
According to the purpose of the utterance there are 4 kinds of SS: 1) The declarative sentence – states a fact in the affirmative or negative form, the subject precedes the predicate, generally pronounced with a falling intonation. The predicate can have only 1 negation. 2) The interrogative S – asks a question, formed by means of inversion (the predicate or part of it is placed before the subject): General Q requiring the answer "yes" or "no" and spoken with a rising int., formed by placing auxiliary or modal verb before the subject; Special Q beginning with an interrogative word and spoken with a falling int., the word order is the same as in GQ, but the interrogative word precedes the verb; Alternative Q indicating choice and spoken with a rising int. in the first part and a falling int. in the second; Disjunctive Q requiring the answer "yes" or "no" and consisting of an affirmative statement followed by a negative Q or vice versa, the first part is spoken with a fall and the second with a rise. 3) The imperative sentence – serves to induce a person to do smth., so it expresses a command (a fall), a request, an invitation (a rise), etc. 4) The exclamatory sentence – expresses emotion or feeling, often begins with the words "what, how", always in the declarative form, generally spoken with a falling int.
According to the structure SS are divided into: 1) A two-member sentence has two members (a subject and a predicate). It can be complete (both members are present) and incomplete (elliptical) (one or both members are missing, but can be easily understood from the context). 2) A one-member sentence has only one member which is neither the subject nor the predicate, one member makes the sense complete, used in descriptions and emotional speech. Mostly expressed by a noun (a nominal sentence) or an infinitive.
1) An unextended sentence consists only of the primary parts. 2) An extended sentence consists of the subject, the predicate and one or more secondary parts (objects, attributes or AM).
More about English grammar can be found via the link supplied.
