Why do people say 'Iru?' alone?


I don't understand why they would say 'Iru?' alone. I thought you needed a
longer sentence for a question.




いる？ is a colloquial way of asking "Want some?" (or "You there?"). Of course
colloquial speech is free to break the usual grammar rules, but even in
standard Japanese grammar both object and subject are optional, so that
answering いる "I want some" (or "I'm here") would be a complete sentence. The
only part that might be disputable in standard grammar is the omission of the
question particle (usually か, but also の), which has been replaced by the
Western question mark (marking rising intonation).

So no, you don't need a longer sentence for a question, certainly not in
colloquial speech.

