Loading
LingakuLingaku若 + [clause]，请 + [verb phrase]
若 + [clause]，(则 / 就) + [clause]
若非 + [noun] / [clause]，[clause]
若 is the written word for "if". It opens the condition, before or after the subject, and belongs in notices, regulations, contracts and essays – anywhere 如果 would sound too conversational.
The result clause often starts with 则, the written partner of 就. The pair is the standard frame for rules, definitions and arguments, where one condition fixes one outcome.
若非 is a negative condition: without X, something else would have happened. The main clause says what that would have been.
In a handful of four-character idioms 若 keeps an older meaning, "like" or "as if". Read it as 像 there, not as "if".
若 sounds stiff between friends. In conversation use 要是 or 如果, and keep 若 for writing and formal announcements.
倘若 and 假若 are more literary versions of the same "if" and have their own point.