ば

There are several different ways to express 'if' in Japanese. One of these is through using the conjunction particle ば. ば presents hypothetical situations (possibilities), and pairs with verbs using an う to え sound-change conjugation method on the terminal (last) kana. Let's examine this with a few verbs first.

• 仕事(しごと)を辞(や)めれば自由(じゆう)時間(じかん)が増(ふ)えるけど、お金(かね)が無(な)くなる。
  If I quit work, I will have more free time, but I will have no money.
• 雨(あめ)が止(や)めば、今日(きょう)も釣(つ)りに行(い)くつもりです。
  If it stops raining, I intend to go fishing today also.
• そこの信号(しんごう)で右(みぎ)に曲(ま)がれば病院(びょういん)に着(つ)きます。
  If you turn right at the light just there, you will get to the hospital.
• 店(みせ)に電話(でんわ)をすれば、すぐに予約(よやく)ができるよ。
  If you call the store, you will be able to make a reservation immediately.
• あいつがくればパーティーが楽(たの)しくなると思(おも)う。
  If he comes to the party, I think it will be more fun.

As we can see with these verbs, the final kana will change to an え sound, from its original う (る to れ, う to え, く to け, す to せ, etc.) before adding ば. It is important to practice these, to not get them mixed up with verbs that use れる, and られる. Unlike with these verbs, the base form of する and くる will not change when using ば.
To conjugate い-Adjectives with ば, the い will be replaced with けれ, one of the standard い-Adjective conjugation forms. After this, just add ば.

• 頭(あたま)が痛(いた)ければ、薬(くすり)を飲(の)んで寝(ね)た方(ほう)がいい。
  If your head hurts, it would be better if you take some medicine and then sleep.
• ラーメン屋(や)のチャーハンが不味(まず)ければ、そこのラーメンも不味(まず)いだろう。
  If a ramen shop's fried rice tastes bad, then the ramen probably tastes bad too, right?

For な-Adjectives, and nouns, なら (another standard conjugation form of these words) will be added, before attaching ば.

• 刺身(さしみ)が嫌(きら)いならば 、寿司(すし)も嫌(きら)いでしょう。
  If you do not like sashimi, then you probably don't like sushi either, right?
• バイクならば、バイク専用(せんよう)の駐輪場(ちゅうりんじょう)に止(と)めてください。
  If it's a motorcycle, please park it in the designated bike parking lot.

In the negative form (using ない), both the auxiliary verb ない, and the い-Adjective ない will conjugate in the same way. Simply replace い with けれ, and then add ば.

• 私(わたし)が作(つく)ったクッキーを食(た)べたくなければ、捨(す)ててもいいよ。
  If you don't want to eat the cookie that I made, you can throw it away.
• カレーが辛(から)くなければ、いっぱい食(た)べれる。
  If the curry isn't spicy, I can eat a lot of it.
• トラックの運転手(うんてんしゅ)でなければ、この仕事(しごと)の辛(つら)さが分(わ)からない。
  If you aren't a truck driver, then you wouldn't understand the hardships of this job.