An interrogative sentence is one that asks a question and requests information, as opposed to a making a declaration, stating a command, or expressing exclamation. Interrogative sentences are easy to spot in writing because they end with a question mark (?), and are usually recognized in speech with an upturn in one's pitch at the end of the sentence.
There are four types of interrogative sentences: yes/no sentences, alternative interrogatives, tag questions, and wh- questions. Yes/no interrogatives are questions that require only a yes or no as an answer, such as Do you like Indian food? Alternative interrogatives as for one of two or more possible responses--Would you prefer chicken or tomato soup? In tag questions, the question is tacked onto the end of a declarative sentence. For instance, You jog every day, don't you? Many interrogative sentences begin with a "question word," also known as wh-words; what, who, where, why, when, and how. For instance, Who are you? When are we leaving? and How do you know that? are all interrogative sentences that begin with question words.
Although interrogatives are different from other sentence types--exclamatory, declarative, and imperative--each of these other types can be turned into interrogative sentences. For instance, Help! is an exclamatory sentence. Simply removing the exclamation point (!) and replacing it with a question mark turns it into an interrogative sentence: help? It looks slightly different and will sound different when spoken. Declarative and imperative sentences must be altered in other ways, in addition to adding a question mark. Most of these sentences, such as He will walk the dog can be made into interrogatory sentences by moving the verb to the beginning of the sentence and adding a question mark: Will he walk the dog?
Finding the subject in an interrogative sentence can be tricky. There is, however, a way to easily find the subject of a sentence--simply rearrange the sentence so that it makes a statement instead of asking a question. This will make the subject, the noun or pronoun performing an action or exhibiting a state of being, easier to locate.