Topic-given conditional — [X] なら, [advice/opinion]
〜なら is the third conditional. It's not about completion (〜たら) or general truth (〜ば) — it's about picking up a topic that's been mentioned (or is in the air) and saying 'if that's the case, then…'. 日本 に 行く なら、京都 が いい です。 = 'If you're going to Japan, Kyoto is good.' The listener has just brought up Japan; the speaker says 'okay, in that case, here's my advice.' That's the 〜なら flavor: 'taking your premise as given, my reaction is…'.
Form — almost no conjugation
〜なら is the easy one. Attach it to plain forms, but for nouns and な-adjectives drop the だ. 行く → 行く なら ('if (you)'re going'). 食べる → 食べる なら. 行った → 行った なら ('if (you) went'). 行かない → 行かない なら. さむい → さむい なら. しずか だ → しずか なら (drop だ). やすみ だ → やすみ なら (drop だ). One pattern, applies everywhere — and it leaves the verb in its plain form, so the time of the X-clause stays whatever you want it.
The 'topic-given' feel — picking up what was just said
Imagine A says: 「今度、日本 に 行きます。」 ('I'm going to Japan soon.') B replies: 「日本 に 行く なら、京都 が いい です よ。」 ('If you're going to Japan, Kyoto is good.') B is taking A's announcement as the premise and giving an opinion based on it. 〜たら would feel weirdly literal here ('once you've gone'); 〜ば would feel too generic. 〜なら signals: 'I'm picking up your topic and reacting to it.' That's why 〜なら loves to come right after someone has set a frame.
〜なら vs. 〜たら — order of events
Here's the sharpest difference. 〜たら = 'once X is done, then Y'. 〜なら = 'if X (is the situation), Y' — and Y can happen before, during, or after X. 日本 に 行く なら、ガイドブック を 買って ください。 = 'If you're going to Japan, please buy a guidebook.' (Y — buying the book — happens before the trip.) 日本 に 行ったら、ガイドブック を 買って ください。 = 'When you're in Japan, please buy a guidebook.' (Y happens after arrival.) Same words, two timelines — 〜なら doesn't lock the order.
Strong with topics and nouns
〜なら is the cleanest conditional for noun topics: 'if (we're talking about) X, then Y.' すし なら、あの レストラン が いい です。 = 'If it's sushi (you're after), that restaurant is good.' アナさん なら、しって います。 = 'Anna? Yeah, I know her.' (lit. 'If (it's) Anna, I know.') The word before なら is the topic the speaker is reacting to. This is why textbooks call 〜なら the 'topical' or 'discourse' conditional.
Common scaffolding
(1) Giving advice / recommendations: 日本 に 行く なら、京都 が いい です。 (2) Hypothesizing about the listener's plan: その 本 を 読む なら、私 の を かして あげましょう か。 = 'If you're going to read that book, shall I lend you mine?' (3) Picking up a topic: すし なら、あの 店。 (4) Counter-suggesting: コーヒー？コーヒー なら、カフェ に 行きましょう。 = 'Coffee? If coffee, let's go to the café.' Notice how 〜なら often follows a just-mentioned word.
The four conditionals — quick map
〜たら = 'once X is done, …' (completion; everyday default). 〜ば = 'given X, …' (general / hypothetical / set phrases). 〜なら = 'if it's the case that X, …' (topic-given; advice). 〜と (later) = 'whenever X, Y inevitably' (mechanical). For now: when someone tells you their plan and you want to react, reach for 〜なら. When you're describing a sequence of events, reach for 〜たら. When you're stating a general truth or set phrase, reach for 〜ば.
