〜場合
in the case of, if
Plain form / Noun + の + 場合(は)
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場合 means "case" or "situation", and 場合は sets a condition: 雨の場合は、試合は中止です, "in case of rain, the match is cancelled".
It's the standard word in rules, instructions, notices and forms: 遅れる場合は、必ず連絡してください, "if you're going to be late, be sure to get in touch". In conversation, たら or なら is more natural.
It follows a plain form, a noun with の, or a な-adjective with な. It's for situations that may or may not happen, not for things that will definitely happen: for "when I get home", use 帰ったら, not 帰る場合.
With a person, it means "in X's case": 私の場合、朝のほうが集中できる, "in my case, I concentrate better in the morning".
Examples
雨の場合は、試合は中止です。
In case of rain, the match will be cancelled.
遅れる場合は、必ず連絡してください。
If you're going to be late, be sure to get in touch.
火事の場合、エレベーターは使わないでください。
In the event of a fire, do not use the lifts.
分からない場合は、係の者に聞いてください。
If anything is unclear, please ask a member of staff.
私の場合、朝のほうが集中できる。
In my case, I can concentrate better in the morning.