았/었어요, ㄹ/을 거예요 and 겠: the past and the future

Start from the 해요 form, because every vowel in it has already merged. Drop 요, tuck ㅆ under the last syllable, then add 어요.

The ㅆ lands on whatever the present left behind, so the contractions carry straight over. 오다 is 와요, so its past is 왔어요. 주다 is 줘요, so 줬어요, and 마시다 is 마셔요, so 마셨어요.

Textbooks write this ending as 았/었어요: 았 after ㅏ or ㅗ, 었 after anything else. That's the same result seen from the stem, as in 앉았어요 and 먹었어요. Whichever way you think of it, the syllable after ㅆ is always 어요.

Pick a verb and switch between present and past. Try 오다 and 주다 to watch a merged vowel keep its shape.

Verbs and adjectives work the same way, and the form doesn't change for who did it. 갔어요 is "I went", "you went" and "she went". Context tells you which.

이다 splits by the sound before it, the way 이에요 and 예요 do. 아니다, 있다 and 없다 are regular.

Some Korean verbs name a change, and the past of that change describes how things stand now. 결혼하다 is the event of getting married, so 결혼했어요 is what a married person says, even twenty years later. English calls that a state and says "am".

You can't predict every one of these, so learn them as you meet them. 잘생겼어요 is the classic trap: it describes someone's face right now, and 잘생겨요 usually sounds wrong.

The future skips the 해요 form. Drop 다 and look at how the stem ends. A vowel takes ㄹ under its last syllable, and a consonant takes 을. Then comes 거예요, as a separate word with a space before it.

ㄹ/을 거예요 says what you expect. About yourself that's a plan, since you're the one deciding. About anything else it's a prediction, and English will often add "probably".

Example 3 has 지금 in it, so it's a guess about right now, with no future in it at all. That's why I think of this form as "expected" rather than "will". After a noun it's 일 거예요, which is 이다 in the same shape.

Korean has a second future marker, 겠. It goes straight on the stem, then takes 어요 or 습니다. Where 거예요 reports something already expected, 겠 comes from this moment: what I'm deciding now, or what I can tell from here.

Said about yourself, it's an intention, and it sounds like a commitment. You'll mostly hear this reading with 습니다, the formal ending from lesson 8, so take those as chunks for now. Weather forecasts use the same form for what's going to happen.

Said about anything else, it's a guess from what's in front of you. You see the food and say 맛있겠어요. You hear about someone's week and say 피곤하겠어요. English reaches for "must" or "looks" here.

You don't always need 거예요. Korean uses the plain present for things already settled, the way English says "I'm leaving tomorrow". A word like 내일 does the work.