What does 제 mean in this sentence?

Question

In the following sentence:

비행기가 제 시간에 출발해요?

What does the 제 mean? It seems to me that my is not the correct usage here...

Answer 1

you are right. 제 has meaning of 'my', but not here. It also has another meaning in '제 시간', '제 정신' and '제 역할'.

"제 + something" indicates not being out of its own purpose or state. So usually, 제 정신 means our mental state for our ordinary life, 제 역할 and 제 시간 correspond to one's role for specific purpose and the time at which something happens, respectively.

ex.1) 제 시간에(제때) 도착해라.

To interpret this simply, it means "Be on time". but basically the sentence means following : You are not to go out of the schedule(to arrive). (시간 as 'schedule')

ex.2) 그는 제 정신이 아니다.

He is insane. but what it basically means is that he is out of his mind. (정신 as 'mind')

ex.3) 그것이 제 역할을 못하고 있다.

It is out of its order. (역할 as 'order')

Answer 2

제 시간에 means 'on time' : (Korean Word A Day examples) so 제 presumably means 'right/proper'. That would also make sense in the expression 제정신, meaning 'of sound mind'.

Answer 3

'제' is not an easy word to understand and it has many meanings. For example:

제가 그 일을 하겠습니다. I will do the job. (You need to note that you should not use '저가' in the sentence. When '가' is suffixed, '저' should be changed to '제' to mean 'I'. Please look at the No. 1 definition below)

제 문제 Various (many) problems.

제2차 세계대전 The Second World War

In order to understand what '제' means in your example sentence, you need to understand what '저' has many meanings, but the two most important meanings are

1. [대명사] 말하는 이가 윗사람이나 그다지 가깝지 아니한 사람을 상대하여 자기를 낮추어 가리키는 일인칭 대명사. 주격 조사 ‘가11’나 보격 조사 ‘가11’가 붙으면 ‘제1’가 된다.

[Pronoun] Polite form of I when speaking to elders (seniors) or unknown people

and

2. [관형사] 말하는 이와 듣는 이로부터 멀리 있는 대상을 가리킬 때 쓰는 말.

[Determiner] A word to point or indicate (towards) something which is far from a speaker and listener.

'제' is a contracted form of '저의' which means 'its' derived from No. 2 definition above. Therefore,

비행기가 제 시간에 출발해요?

could be literally translates to

Will the plane depart on its (scheduled) time?

'제정신' could be translated to 'his/her mind' when you say "그는 제정신이 아니다" which literally means "He is not his mind"

'제 역할' is somewhat different. '제' could also mean 'various (many)'.

You should note that '제' has many meanings and it should be understood based on context. Also, you need to write '제시간' without a space between '제' and '시간'.