Conditionals

إذا (when, if) takes the past in both parts, even for the future: إذا درست نجحت. It is the usual word for a likely condition.

إن (if) takes the jussive, which drops the ن like لم: إن تدرسوا تنجحوا. When the answer is a noun sentence, a command or starts with سوف, it opens with ف: إن جئت فأنا في البيت.

لو (if only it were) is for an unreal condition. It takes the past, and its answer starts with ل: لو درست لنجحت. The negative answer uses ما: لو عرفت ما ذهبت.