ば

ば is the conditional "if": when the first half holds, the second half follows from it. It is a verb ending, not a word that follows the plain form. A verb's last sound moves from the う-row to the え-row and takes ば (いけば行けば, たべれば食べれば, すれば, くれば来れば); an い-adjective swaps い for ければ (やすければ安ければ); a noun or a な-adjective takes であれば or なら.

ば puts the weight on the condition: this is what it takes for the result to happen. A negative condition is なければ, "unless".

Requests and plans after ば

When the ば half is an action and the same person does both halves, the second half cannot be a request, an order or a plan. Use たら there.

• × 駅に着けば、電話してください → 駅に着いたら、電話してください

When the ば half is a state – ある, いる, an adjective, a negative – the second half can be anything.

ば, たら, と and なら

The four overlap but are not interchangeable. と says the result follows automatically, every time, and never takes a request. たら is the everyday "if" and "once", and takes anything after it. なら picks up something just said: "if that's the case". ば sits nearest to と but stresses the condition rather than the sequence.

Usage notes

These go beyond the plain conditional. Each is its own grammar point.

Regret: 〜ばよかった

With よかった, ば looks back at what you didn't do.

Advice: 〜ばいい

With いい, it says what would do the job.

"The more…": 〜ば〜ほど

The same verb in ば and then before ほど.

Proverbs

Proverbs keep an older ば that attaches to the ない-stem: いそが急がばまわれ回れ, "more haste, less speed". Don't copy it into a modern sentence.