たらいい details
write + (past) + it'd be good if you did
kaita raii
it'd be good if you did; I hope — advice for this situation, or a wish about something no one controls
meaning: it'd be good if you write
分からなかったら、先生に聞いたらいいよ。
wakaranakattara, sensei ni kiita raii yo.
If you don't get it, it'd be good if you ask the teacher. casual
頭が痛いなら、この薬を飲むといいよ。
atama ga itai nara, kono kusuri o nomu to ii yo.
If you have a headache, it'd be good to take this medicine. casual
- formal
- polite
Examples
it'd be good if you did — advice scaled to the one situation the speaker has in mind (たらいい)
分からなかったら、先生に聞いたらいいよ。
wakaranakattara, sensei ni kiitaraii yo.
If you don't get it, it'd be good if you ask the teacher. casual
風邪なら、早く寝たらいいですよ。
kaze nara, hayaku netaraiidesu yo.
If it's a cold, it'd be good if you sleep early. neutral
書類はどちらにお送りしたらよろしいでしょうか。
shorui wa dochira ni o okuri shitara yoroshii deshou ka.
Where would it be best to send the documents? formal
it'd be good if you did; I hope — といい's two faces, advice about the listener's situation and a wish about an outcome nobody controls
頭が痛いなら、この薬を飲むといいよ。
atama ga itai nara, kono kusuri o nomu to ii yo.
If you have a headache, it'd be good to take this medicine. casual
明日晴れるといいな。
ashita hareru to ii na.
I hope it's sunny tomorrow. casual
手術がうまくいくといいですね。
shujutsu ga umaku iku to ii desu ne.
I hope the surgery goes well. neutral
Formation
{V-ta}らいいattaches to た-form{V}といいattaches to dictionary form
Variant notes
- たらよろしい — よろしい is the formal stand-in for いい — 書類[しょるい]はどちらにお送[おく]りしたらよろしいでしょうか — common in service and business language.
Notes
ないといいね. といい's WISH sense almost always closes with ね, since a bare
wish left unshared reads oddly; its advice sense takes よ instead.
Related patterns
Similar
Inside the いい frame, general-vs-one-off mostly neutralizes — どうすればいい and どうしたらいい read as near-equivalents — but real asymmetries remain. ばいい can land curt, "that's all you need to do"; たらいい reads softer and more colloquial; といい is the conventionalized wish form (defaults to ね), though all three can voice a wish.
Lookalikes
The と inside といい is not the automatic-consequence と of 押[お]すと — きれいになるといいね is a wish about an outcome no one controls, not a lawlike trigger-and-result pair, so と alone cannot substitute for it.