[Serie: All About Japanese Particles]
Note: See also mono nara (#37).
1. Indicates a supposition and result: “if … then.”
Note: Nara is often used after nouns. It is similar to -ba (#34, no. 1), -tara (#35, no 1), and to (#6, III-3).
私は午後なら暇がありますよ。
Watashi wa gogo nara pima ga arimasu yo.
If [it’s in] the afternoon, I’m free. / I’ll be free in the afternoon.
明日雨なら、ゴルフに行かないつもりです。
Ashita ame nara, gorufu ni ikanai tsumori desu.
Tomorrow, if it’s raining, I don’t intend to go golfing. / I don’t plan to go golfing tomorrow if it rains.
あの人が行くなら、私は行きたくないですね。
Ano hito ga iku nara, watashi wa ikitaku nai desu ne.
If she’s going, I sure don’t want to.
Note: A major difference between nara and -tara is that the clause after nara emphasizes what would (definitely) take place if the supposed event were to occur, whereas the result clause after -tara emphasizes what would “happen to” take place.
乗るなら飲むな。飲んだら乗るな。
Noru nara nomu na. Nondara noru na.
If you [are going to] drive, don’t drink. If you have been drink-ing, don’t drive.
2. Indicates that a topic is being brought up: “as for.”
その問題なら、もう解決しました。
Sono mondai nara, mō kaiketsu shimashita.
As for that problem, it had already been settled.
和歌の参考書なら、佐々木先生の研究室にある。
Waka no sankosho nara, Sasaki-sensei no kenkyū-shitsu ni aru.
If it’s reference books on waka [that you’re looking for], they’re in Professor Sasaki’s office.
– Source: All about particles – A handbook of Japanese function words –