Forming a Sentence
There are two ideas which are prevalent throughout the Korean language. Firstly, the order of information is organized from general to specific. Secondly, implicitly understood information can be ommitted from communcation.
A simple Korean sentence is composed of a subject and a predicate. The subject is written before the predicate.
If the predicate accepts an object, then the object is written before the predicate.
Context based omission
The subject or topic of a sentence can be omitted when the subject or topic is implicitly understood. Pronouns are the most commonly omitted parts of speech in Korean communication.
덕수: 선미 ?Duksu: Has Sunmi eaten?
선미: . .Sunmi: (I) have not eaten. (I) am hungry.
As for Sunmi's response, notice that neither the first sentence (안 먹었어요) nor the second sentence (배고파요) has an explicit subject.