〜場合は、〜 (~baai wa, ~) — In the case of ~

Grammar rule (व्याकरण नियम र परिभाषा)

「場合」means "case" or "situation". 「〜場合は」says "if this situation comes up, do this". That is why you meet it most in company rules, notices, manuals and safety instructions. **How it attaches to the six kinds of word:** the dictionary form (辞書形) of a verb — 遅れる 場合は (a situation that may still happen). The た form of a verb — 機械が 止まった 場合は (a situation that has already happened). The ない form of a verb — 分からない 場合は. An い-adjective attaches directly — 都合が 悪い 場合は. A な-adjective needs な — 必要な 場合は. A noun needs の — 病気の 場合は. **Two things to remember:** first, the dictionary form and the た form differ in timing — 遅れる 場合は is "if you may be late", 遅れた 場合は is "if you have already become late". Second, 「とき」points at a definite time (日本へ 行く とき、切符を 買います), while 「場合」points at a situation that may or may not happen, so 場合 does not fit things that always happen. A request, an order or an instruction can all follow 場合は. Which to pick? Use 場合は for rules, notices and work instructions. In ordinary talk with a friend たら is enough — 遅れたら、電話して ください is fine too, but 遅れる 場合は sounds more formal.