This is the 6243rd most frequent Korean word.
시에는
"시에는" means "at the time" or "during."
In this sentence, "시에는" indicates the specific period or activity of studying during which attention is required.
공부하는 시에는 집중해야 합니다.
You must focus while studying.
Here, "시에는" marks the time of engaging in exercise, suggesting appropriateness for the action mentioned.
운동하는 시에는 물을 충분히 마셔야 합니다.
You should drink enough water while exercising.
"시에는" signifies the time defined as lunchtime, connecting it to the action of eating.