Verb provisional form + ば — 'given X, Y'
Japanese has a second core conditional: 〜ば. Where 〜たら says 'once X is done', 〜ば says 'given X, …' — it's the conditional for general truths, natural consequences, and hypotheticals about how the world works. 春 に なれば、桜 が さきます。 = 'When spring comes, the cherry blossoms bloom.' Form: shift the final syllable of a verb from the u-row to the e-row, and add ば. 行く → 行け + ば → 行けば ('if (one) goes'). For る-verbs: drop る, add れば → 食べれば. For い-adjectives: drop い, add ければ → さむければ. We'll handle each shape below.
う-verbs (Group 1) — shift to the e-row
Take the dictionary form, slide the final kana from the u-row to the e-row, and add ば. 行く (iku) → 行け (ike) + ば = 行けば. 読む (yomu) → 読め + ば = 読めば. はなす → はなせ + ば = はなせば. のむ → のめ + ば = のめば. かう (kau) → かえ + ば = かえば. まつ → まて + ば = まてば. The same e-row shift you used for potential form (lesson 16) — same column, then add ば instead of る.
る-verbs (Group 2) — drop る, add れば
Easier. 食べる → 食べ + れば = 食べれば. 見る → 見 + れば = 見れば. ねる → ね + れば = ねれば. おきる → おき + れば = おきれば. Just chop る, glue れば.
Irregulars and negatives
する → すれば. 来る → くれば. Negatives use 〜ない → drop い, add ければ (just like an い-adjective): 行かない → 行かなければ ('if (one) doesn't go'). 食べない → 食べなければ. しない → しなければ. 来ない → こなければ. The negative form gives you the famous 〜なければ なりません = 'must do' = literally 'if (one) doesn't, it won't do'.
い-adjectives and nouns / な-adjectives
い-adjectives: drop い, add ければ. さむい → さむければ ('if it's cold'). おいしい → おいしければ ('if it's tasty'). やすい → やすければ. The exception いい uses its older base よい → よければ ('if it's good'). For nouns and な-adjectives, the ば-form is built differently and rarely used in modern speech — most speakers swap in 〜なら (next lesson) or 〜だったら. So: 〜ば is mainly a verb and い-adjective thing in everyday Japanese.
When to reach for 〜ば
(1) Universal / natural truths: 春 に なれば、桜 が さきます。 = 'When spring comes, the blossoms bloom.' (always true) (2) General hypotheticals: やすければ、かいます。 = 'If it's cheap, I'll buy it.' (a rule about my behavior) (3) 'All you have to do is X': この ボタン を おせば、いい です。 = 'You just have to press this button.' / しんぱい しなければ、だいじょうぶ です。 = 'If you don't worry, you'll be fine.' (4) Counterfactuals / wishes: お金 が あれば… = 'If only I had money…'. Pair with いい for 'I wish': 雨 が やめば いい です ね。 = 'It'd be nice if the rain stopped, wouldn't it.'
〜ば vs. 〜たら — a sharper contrast
Both can mean 'if', but 〜ば is timeless / general, while 〜たら is event-completion / specific. 時間 が あれば、行きます。 ≈ 'If I have time, I'll go.' (general policy) 時間 が あったら、行きます。 ≈ 'If I have time (this Saturday), I'll go.' (specific occasion) Both work in many sentences; the feel differs. 〜ば also wins for set phrases and proverbs: 見れば わかる。 = 'You'll get it if you (just) look.' 〜たら wins for definite future sequences ('once X happens, then Y'). When in doubt in spoken Japanese, 〜たら is safer; 〜ば sounds slightly more bookish or aphoristic.
〜ば いい = 'should' / 'just need to'
A high-mileage pattern: 〜ば いい です = 'you just need to (do X)' / 'it's enough if you (do X)'. わからなければ、きけば いい です。 = 'If you don't understand, just ask.' (きく → e-row → きけ + ば = きけば.) どう すれば いい です か。 = 'What should I do?' (literally 'if I do how, will it be good?'). Memorize どう すれば いい です か as one chunk — it's the polite way to ask 'what should I do?'.
