Like many languages, Korean has a lot of grammar that just dictates how we talk about time. There are so many forms and this article discusses yet another one. The Korean time expression for this article is 때 which can end up being a bit difficult initially to understand.
The form 때 is a Korean time expression that indicates when an action or state takes place or the duration of said action or state. This often causes confusion as to what the difference is between it and -에. Many times there is even little difference between the two when speaking about when something takes place. However, keep in mind that -에 is only an option with a specific time and nouns for it, not with a duration of time. For the duration and nouns with which -에 would be weird, you can use 때.
가: 옷이 많이 더러워요. 세탁할게요.
나: 실크라서 세탁할 때 조심하세요.
A: Your clothes are very dirty. I’m going to wash them.
B: It’s silk, so be careful when you wash it.
How To Use
Using 때 with nouns is very easy. You simply have to write it behind the noun (unattached) and you are done with it. However, keep in mind you cannot use it with a select few nouns. The most important nouns that cannot be used with it are 아침 (morning), 오전 (morning), 오후 (afternoon), 일요일 (Sunday), 월요일 (Monday), 화요일 (Tuesday), 수요일 (Wednesday), 목요일 (Thursday), 금요일 (Friday) and 토요일 (Saturday).
You can also use 때 with verbs and adjectives, but to use it with them the form becomes -(으)ㄹ 때. The rules are pretty simple as it is a simple ‘batchim/no batchim’ situation. When the verb stem ends in batchim (consonant), you have to use -을 때. However, if it ends in no batchim (vowel), you’ll have to use -ㄹ 때. Also, don’t forget your Korean irregular verbs like the ㅂ irregular verbs and the ㄷ irregular verbs. There is little else to it so it isn’t such a complicated Korean grammar topic.