~れば / ~ば, ~たら (conditional forms)

To make the ~ば form of an Ichidan verb, add ~れば to the verb base. To make the ~ば form of a Godan verb, use the "e" formative and add ~ば. To make the ~たら form of any verb use the past form and add ~ら. Because conditional forms are used as conjunctions, there is no formal conditional form. The level of politeness is determined by the final verb of the main clause:

Ichidan - Vowel Stem Verbs
見る [miru] 見れば [mireba] 見たら [mitara]
出る [deru] 出れば [dereba] 出たら [detara]
Godan - Consonant Stem Verbs
話す [hanasu] 話せば [hanaseba] 話したら [hanashitara]
飛ぶ [tobu] 飛べば [tobeba] 飛んだら [tondara]
読む [yomu] 読めば [yomeba] 読んだら [yondara]
死ぬ [shinu] 死ねば [shineba] 死んだら [shindara]
聞く [kiku] 聞けば [kikeba] 聞いたら [kiitara]
泳ぐ [oyogu] 泳げば [oyogeba] 泳いだら [oyoidara]
待つ [matsu] 待てば [mateba] 待ったら [mattara]
習う [narau] 習えば [naraeba] 習ったら [narattara]
座る [suwaru] 座れば [suwareba] 座ったら [suwattara]
Henkaku - Irregular Verbs
する [suru] すれば [sureba] したら [shitara]
来る [kuru] 来れば [kureba] 来たら [kitara]
行く [iku] 行けば [ikeba] 行ったら [ittara]

~ば is used when the condition is more hypothetical, and often emphasizes the condition.

  1. あたためたぎゅうにゅうめばねむくなる。 If you were to drink warm milk you would get sleepy.
  2. ほんったときともだちができればよかった。 It would have been nice if I could have made friends when I went to Japan.

~たら is used when the condition is more concrete, and often emphasizes the sequence.

  1. あたためたぎゅうにゅうんだらねむくなる。 If you drink warm milk you will get sleepy.
  2. ざんぎょうがなかったらえいきます。 If I don't have overtime I go see a movie.

When the main clause is a request/demand, and the conditional clause is an action use ~たら.

Incorrect: もくてきけばれんらくしてください。 Correct: もくてきいたられんらくしてください。

Otherwise you can use either ~ば or ~たら.

Correct: かんがあればください。 Correct: かんがあったらください。

The particles なら and と can also be used to express condition.