In short

This is the family for wishing and for looking back with regret. To wish, cap a condition clause with 좋겠다: 시간이 있으면 좋겠어요 (sigani isseumyeon jokesseoyo, I hope I have time). To regret your own past choice, use -(으)ㄹ걸 그랬다 (올걸 그랬어요, I should have come). For the full “if only… would have” counterfactual, pair -았/었더라면 with -았을 텐데 (일찍 출발했더라면 안 늦었을 텐데요). Near-misses take -(으)ㄹ 뻔했다 (넘어질 뻔했어요, I almost fell).

The rule

Step 1 - Wishes: -(으)면 좋겠다

A wish is a condition clause plus 좋겠어요 (jokesseoyo, it would be nice). Take the -(으)면 conditional from lesson 29 and cap it: 시간이 있으면 좋겠어요 (sigani isseumyeon jokesseoyo, I hope I have time). Two shades:

• Plain -(으)면 좋겠다 = a hope that is still open and reachable.
• Past -았/었으면 좋겠다 = a wistful wish, often against present reality: 부자였으면 좋겠어요 (bujayeosseumyeon jokesseoyo, I wish I were rich - but I’m not). The -았/었- here is hypothetical, not real past; in speech Koreans reach for this past-marked version even for perfectly reachable wishes, so 왔으면 좋겠어요 (wasseumyeon jokesseoyo, I hope it comes) is the everyday default.

Unlike -고 싶다 (lesson 26), which needs your own action (“I want to go”), -(으)면 좋겠다 can wish for anything - the weather, other people, being something - because the wish is a whole clause, not your verb. Note it is 좋겠어요, not 좋아요: the -겠- turns “it’s good” into “it would be good / I wish.”

Step 2 - Regret over your own choice: -(으)ㄹ걸 (그랬다)

To kick yourself over a past decision, attach -(으)ㄹ걸 to the plain verb stem and follow with 그랬다: 일찍 올걸 그랬어요 (iljjik olgeol geuraesseoyo, I should have come earlier). The stem stays plain - the pastness lives in 그랬어요 - so it is 올걸, never *왔을걸. For the opposite regret (“I shouldn’t have”), use -지 말걸 그랬다: 하지 말걸 그랬어요 (haji malgeol geuraesseoyo, I shouldn’t have done it). In speech 그랬어요 is often dropped and the ending just trails off: 올걸…

Beware the look-alike: -(으)ㄹ걸요 is not regret but a soft guess - 벌써 갔을걸요 (beolsseo gasseulgeollyo, they’ve probably already left), 아마 집에 있을걸요 (ama jibe isseulgeollyo, they’re probably home). Same shape, opposite job; 그랬다 is the reliable marker of the regret reading, while the guessing one ends in 요 - and a tensed stem (갔을걸요) can only be the guess, since the regret never takes one.

Step 3 - The full counterfactual: -았더라면 … -았을 텐데

For “if only X had happened, Y would have” - a situation you can no longer change - put -았/었더라면 on the if-clause and cap the result with -았을 텐데(요) (regret) or -았을 거예요 (plain “would have”):

[past stem] + 더라면, … [past stem] + 을 텐데 -> 일찍 출발했더라면 안 늦었을 텐데요 (iljjik chulbalhaetdeoramyeon an neujeosseul tendeyo, if I’d left early, I wouldn’t have been late). Both halves are past-loaded because the whole sentence is contrary to fact. This is the heavyweight cousin of plain -(으)면 (lesson 29), which leaves the condition open and reachable; the -(으)ㄹ 텐데 result half comes from lesson 47.

Step 4 - Near miss: -(으)ㄹ 뻔했다

Attach -(으)ㄹ 뻔했다 (뻔하다 is an auxiliary, so it takes a space after the -(으)ㄹ form) for something bad that almost happened but didn’t: 넘어질 뻔했어요 (neomeojil ppeonhaesseoyo, I almost fell); 큰일 날 뻔했어요 (keunnil nal ppeonhaesseoyo, that was a close call). It is fixed in the past 뻔했다 - the near-miss is, by definition, already over - so never *뻔해요. It is the language of relief: “phew, I nearly…”.

Step 5 - Should have: -았어야 했는데

Built on the -아/어야 obligation from lesson 34, a past-stem -았/었어야 했는데(요) says you should have done something and didn’t: 미리 예약했어야 했는데요 (miri yeyakhaesseoya haenneundeyo, I should have booked ahead). The blunter spoken reproach, aimed at someone else, is -았/었어야지요: 미리 말했어야지요 (miri malhaesseoyajiyo, you should have told me first).

Forms & patterns

Wishing with 좋겠다 (the condition is an ordinary -(으)면 clause):

Regret -(으)ㄹ걸 그랬다 - which allomorph (attaches to the plain stem; 그랬다 carries the past):

The regret / counterfactual toolkit at a glance:

Examples

Common mistakes

• 비가 오고 싶어요. (biga ogo sipeoyo) -> 비가 왔으면 좋겠어요. (biga wasseumyeon jokesseoyo) - -고 싶다 is only for your own wanted action, so *비가 오고 싶어요 says “the rain wants to come.” A wish about the weather (or anyone else) uses -(으)면 좋겠다.
• 시간이 있으면 좋아요. (sigani isseumyeon joayo) -> 시간이 있으면 좋겠어요. (sigani isseumyeon jokesseoyo) - plain 좋아요 states a fact (“it’s nice when I have time”); to voice the wish you need the -겠- of 좋겠어요.
• 일찍 왔을걸 그랬어요. (iljjik wasseulgeol geuraesseoyo) -> 일찍 올걸 그랬어요. (iljjik olgeol geuraesseoyo) - the regret -(으)ㄹ걸 그랬다 takes the plain stem; the past already lives in 그랬어요, so don’t also mark 왔을. (Tensed 왔을걸요 exists, but that’s the guessing ending.)
• 일찍 출발하더라면 안 늦었을 텐데요. (iljjik chulbalhadeoramyeon…) -> 일찍 출발했더라면 안 늦었을 텐데요. (iljjik chulbalhaetdeoramyeon…) - the counterfactual needs the past stem -았/었더라면 (했더라면), not a bare -더라면.
• 넘어질뻔했어요. (neomeojilppeonhaesseoyo) -> 넘어질 뻔했어요. (neomeojil ppeonhaesseoyo) - 뻔하다 is an auxiliary (보조 형용사) hanging off the -(으)ㄹ modifier form, and the dictionary itself cites it as “-을 뻔하다”, so the standard spelling keeps the space, exactly like 할 수 있어요 and 갈 것 같아요.

Tips

• “I want to” vs “I wish.” If you can phrase it in English as I want to [verb] with your own action, use -고 싶다. If it’s a state of affairs you wish were true - the weather, someone else, yourself being something - use -(으)면 좋겠다.
• One shape, two jobs for -(으)ㄹ걸. Plain stem + -(으)ㄹ걸 그랬다 (or trailing off, 올걸…) is self-directed regret; -(으)ㄹ걸요 on a tensed or plain stem (갔을걸요, 있을걸요) is a soft guess about someone else. 그랬다 - and the 요 on the guessing one - keep them apart.
• The “if only” template is all past. -았더라면 … -았을 텐데(요) / -았을 거예요 - both halves carry a past because the whole thing is contrary to fact. Contrast plain -(으)면 (lesson 29), which is a real, still-open condition.
• -(으)ㄹ 뻔했다 is always about a bad thing that didn’t happen. It is fixed in the past (뻔했다, never *뻔해요) and expresses relief - the near-disaster was narrowly avoided.