Mita-san-no bun-mo chanto totte-aru-kara. (We were careful to leave you your share.)

Situation 1: A group of young colleagues are eating and drinking at a pub. Mr. Mita arrives late.

三田： ああ、お腹がぺこぺこだよ。まだ食べるもの、 残っている？

グレイ： 大丈夫。三田さんの分もちゃんと取ってあるから。

Mita: Ā, onaka-ga pekopeko-da-yo. Mada taberu-mono, nokotte-iru?

Gurei: Daijōbu. Mita-san-no bun-mo chanto totte-aru-kara.

Mita: Oh, I'm dying of hunger. Is there anything left to eat?

Gray: Don't worry, we were careful to leave you your share.

Today we will introduce some expressions using 分(ぶん), which means "share," "part" or "portion." The structure X分 expresses "something for X" or "something equivalent to X," when X is number+counter, noun+の or a verb in noun-modifier form. Examples: お弁当(べんとう)を５人分(ごにんぶん)用意(ようい)した (I prepared lunch boxes for five people); 残(のこ)った分はあとで食(た)べよう (Let's eat the leftovers later); 今月分(こんげつぶん)のバイト代(だい)はあした払(はら)います (I'll pay you for this month's part-time work tomorrow).

Situation 2: Continued from Situation 1, as they finish eating.

三田： あーあ、今日(きょう)は食べ過ぎちゃった。体重、 増えるかな。

セレ： もちろん、食べた分だけ太るよ。あしたから運動でもやって、その分の体重を減らすんだね。

Mita: Āa, kyō-wa tabesugichatta. Taijū, fueru-kana.

Sere: Mochiron, tabeta bun-dake futoru-yo. Ashita-kara undō-demo yatte, sono bun-no taijū-o herasu-n-da-ne.

Mita: Oh, I ate too much today. Do you think I'll put on weight?

Sere: Of course, you'll put on as much weight as the food you eat. You should do a bit of exercise or something tomorrow so that you lose the weight you've gained.

X分(ぶん)(だけ)Y means "Y as much as X" and communicates that Y will progress by an amount equivalent to or in proportion with X. Examples: アパートが駅(えき)から近(ちか)い分だけ、家賃 (やちん)も高(たか)くなる (The closer to the station the apartment is, the more expensive the rent is); 練習(れんしゅう)した分(ぶん) だけ日本語(にほんご)が上手(じょうず)になります (Your Japanese will improve by as much as you practice.). この分 means "as things stand now" or "at this rate" and is usually used in the patterns この分では, この分でいくと or この分なら, as in: この分では試験(しけん)に合格(ごうかく)できないよ (At this rate, you won't pass the exam). この分なら usually has a positive meaning, as in この分なら仕事(しごと)は早(はや)く終(お)わるだろう (As things are going now, the work will be finished quickly).

Bonus Dialogue: Ms. Shiba, who has a small child, tells Mr. Tian that she will have to go home early. (Note: In these kinds of conversations in Japanese, the gender of the child is not necessarily specified.)

芝： 子供(こども)が病気(びょうき)で、今日は３時(さんじ)に帰(かえ)らなくちゃならないんです。

ティエン： ああ、それは心配(しんぱい)ですね。

芝： ええ。でも、仕事(しごと)は今日の分(ぶん)をやって おきましたから、大丈夫(だいじょうぶ)です。

ティエン： そんなに気(き)をつかわなくてもいいですよ、お子(こ) さんが小(ちい)さいときは。たとえば食事(しょくじ)も 大変(たいへん)でしょう？

芝： そうですね。子どもの分を別(べつ)に作(つく)らなくちゃならないから、手間(てま)がかかるんです。

ティエン： そうですか。

芝： でも、元気(げんき)に育(そだ)っているから、この分で いけば、もうすぐ大人(おとな)と同(おな)じになります。早(はや)く３人分(さんにんぶん)の同じ食事を作るようになりたいなあ。

ティエン： がんばった分だけ、いいことがありますよ。

芝： そうかもしれないですね。そう思(おも)いたいです。

Shiba: My child is sick, so today I'd best go home at 3.

Tian: Oh, you must be worried.

Shiba: Yes. But it's all right, I've already done today's share of the work.

Tian: You don't have to worry so much about all this work stuff while your child is so small. For one thing, cooking must be a hassle, right?

Shiba: Yes. I have to cook my child's share separately, and it takes a lot of time and effort.

Tian: Oh, really?

Shiba: But (s)he's growing healthily, and at this rate (s)he'll soon be eating the same as us adults. I'm looking forward to being able to cook the same meal for three.

Tian: The more effort you put in, the more good things will happen to you!

Shiba: Perhaps you're right. I want to believe that.