A question is a group of words in interrogative form which calls for an answer. In this sense, inquiry is interchangeable with question : an impertinent question answered with steely silence; an inquiry to a hotel manager about the tariff for a suite of rooms. Inquiry can go beyond this simple meaning to refer to a group of questions, a search for knowledge or information by observing, experimenting, etc., or a full-scale, official investigation: the desk handling inquires about share prices; a thorough inquiry into the nature of a particular physical phenomenon; a departmental inquiry into a alleged breach of security. Query can be used as a synonym for question or the corresponding sense of inquiry . The word has a slightly formal or literary tone and is best used when the question being asked is an attempt to clear up some doubt or indecision, or when there is an indication of a genuine search for specific or authoritative information: to make a query only when the meaning of a passage is not perfectly evident; a serious query of such complexity that it had to be referred to the chairman of the town-planning authority. It is often, indeed, the seriousness of intent on the part of the person who poses a question that makes the question a query . Questions are sometimes designed merely to perplex, confuse or entrap the person of whom they are asked; queries are never so idle or frivolous. Enquiry is an alternative spelling of inquiry , preserved by some users for a special context (for example to refer to a question asked), but a fixed rule would be useless.

These words refer to the asking or demanding of information. Of these, question is the most general in meaning and the most neutral in tone. At its most restricted, it may be used as a more formal substitute for ask, in the sense of making a single or specific query: questioning the woman at the information desk about where he could exchange certain goods. More pertinent here, is its use to suggest the asking of a series of questions to bring information to light: questioning the witnesses for details about the physical appearance of the murderer. It may suggest an informal situation: questioning him about why he was so late getting home from work. Often, the word points to an official or formal situation: The suspect was brought to the police station to be questioned about his connections with the deceased man. Interrogate is a much more formal substitute for question and is mostly restricted to an official examination of some sort: warning him that the police prosecutor would interrogate him about matters that might embarrass him.

Grill , by contrast, is a much more informal word commonly used in the United States; it applies specifically to intensive interrogating in which someone is subjected to pressure to reveal information: a dozen petty criminals who had been rounded up and grilled for hours about their activities on the night of the hold-up. The pressure may be psychological, but can extend to physical torture: grilling the captured guerrilla by the water-torture method. Quiz suggests the use of much less strenuous means than grill and may apply to more ordinary situations; it does suggest intensive questioning : quizzing her children about every move they had made while she was gone. Often the word suggests an educational context, referring in this case to short informal tests, oral or written, conducted to determine the mastery of assigned work: quizzing the students twice a week on their outside reading.