The izenkei conjugation (已然形) is also called the hypothetical form and has only one function in modern Japanese: combined with + ば (ba) it is one of several conditional forms, translated as "if" or "when". No contractions occur with the izenkei. Find more information on the use of the izenkei + ば (ba) construction below.

Izenkei conjugations

Group 2 conjugationsto eatto se
Rentaikei食べる taberu見る miru
Izenkei食べれ tabere見れ mire

Group 4 conjugationsto writeto buyto waitto lend
Rentaikei書く kaku買う kau待つ matsu貸す kasu
Izenkei書け kake買え kae待て mate貸せ kase

Irregular verbsto doto come
Rentaikeiする suru来る kuru
Izenkeiすれ sure来れ kure

Verbal adjectivesto be largeto be new
Rentaikei大きい ōkii新しい atarashii
Izenkei大きけれōkikere新しけれ atarashikere

Verbal adjectiveto be good (irregular)
Rentaikeいい/良い (ii / yoi)
Izenkeiよけれ/良けれ (yokere)

All verbs have a regular izenkei conjugation.

Izenkei + ba (ば)

The izenkei conjugation has only one function in modern Japanese. Combined with + ば (ba) it is one of several conditional forms, translated as "if" or "when". The izenkei + ば (ba) is used when there is a logical cause and effect relation.

The izenkei + ば (ba) can also be used to describe an observation or conclusion. In this case it can be translated as "Now that I…" [often encountered as ren'youkei + てみれば (te mireba)], as "when" or "while", describing a coincidence or one-off occurrence (used as とき toki), or as "and then" when actions are performed by the same grammatical subject.

The izenkei + ば is never found at the end of a sentence. It always ends the conditional clause, followed by the main clause.

Takakereba kaenai.
If it's expensive, I can't buy it.

Setsumei wo yonde mireba sugu wakarimasu.
When you've read the instructions, you will understand.

Dou sureba ii deshou ka.
What would be the best way to do this? (Literally: If I do it now, will it be ok?)

だ (da)

The verb だ (da) doesn't have an izenkei conjugation; it is therefore not possible to contract である (de aru) into だ (da).

Present tense Conditional form
ある aru あれば areba
である de aru であれば de areba
だ da であれば de areba
です desu であれば de areba
Izenkei + ばならない (ba naranai) / + ばいけない (ba ikenai)

Special combinations are the izenkei + ばならない (ba naranai) or the izenkei + ばいけない (ba ikenai). These combinations form a prohibitive, and are translated as "mustn't". When using the double negatives mizenkei + なければならない (nakereba naranai) or mizenkei + なければ行けない (nakereba ikenai) these combinations form an imperative, and are translated as "must" or "have to".

Sono you na hon wo yomeba ikenai.
You mustn't read a book like that.

Sugu ikanakereba naranai.
I must leave soon.