As in English, the Arabic conditional verb tense is used in if/then situations. If one thing does, doesn’t, or did happen, another thing will, won’t, or would happen. The second event is contingent on the first. However, unlike in English, there are two primary ways to say “if” in Arabic: لو and اذا.

As a general rule, لو applies to permanent or irreversible situations and اذا is used when the situation has not yet happened or could be changed. In other words, if you had or hadn’t done something, go with لو . If you might or might not do something, go with اذا. Understandably though, there’s a lot of gray area in which either لو or اذا would be correct.

The other tricky aspect of the Arabic conditional tense is that many of the words we use to convey the conditional in English do not have direct translations in Arabic. In Ammiyeh, conditional statements do not require a word for “then,” nor even a comma to distinguish between the two clauses of the sentence:

لو سكنت ببيت ستي وكبرت بدمشق كنت حكيت العربي
If I had lived at my grandma’s house and grown up in Damascus[,] I would speak Arabic

Arabic also doesn’t have an equivalent word for “had”, “have” or “would”. Instead, the shades of meaning that these words impart in English are conveyed based on whetherلو or اذا is used, and how the other verbs in the sentence are conjugated (past, present, or future tense).

Basic structure of لو and اذا phrases:

لو + الفعل بالماضي + كان + الفعل بالماضي
Law + a past tense verb + kan (in the appropriate form) + a verb in the past tense
The second kan in this structure is sometimes omitted

اذا + الفعل بالماضي او بالمضارع + رح الفعل بالمضارع
Iza + a verb in the past or the present tense + future indicator + verb in the present tense

Let’s look at an example of the same situation - one sentence with لو and one with اذا - and compare their meanings:

لو شفت المسلسل مبارح كنت عرفت شو صار بالقصة
If I had seen the show yesterday, I would have known what happens in the story

اذا شفت المسلسل رح بعرف شو بيصير بالقصة
If I saw the show I would know what happens in the story

Both statements start in the past: “if I had watched…” The difference is what is possible now and in the future. The first sentence describes watching the show yesterday which is no longer possible because yesterday has already happened. So, by using لو in the first sentence, we are communicating that watching the show is no longer possible. By using اذا in the second sentence, we leave open the possibility that I could watch the show now or in the future. I haven’t watched the show yet, but the opportunity to do so has not passed.

A few more examples:

لو أكلتي الدجاج كنتي مرضتي
If you (fem.) had eaten the chicken, you (fem.) would have gotten sick
اذا بتاكلي الدجاج رح تمرضي
If you (fem.) eat the chicken, you (fem.) will get sick

لو هي حبته كانت تزوجته
If she had loved him, she would have married him
اذا هي بتحبه رح تتزوجه
If she loves him, she will marry him

لو تدربت أكتر كنت أقوى بكتير
If I had exercised, I would be a lot stronger
In sentences like this one where you would have a double kan (كنت كنت أقوى), the second kan is eliminated
اذا بتدرب أكتر رح أصير أقوى بكتير
If I exercise more, I will become a lot stronger

لو ما قال شي ما كنا رحنا عالسجن
If he hadn’t said anything, we wouldn’t have gone to jail
اذا ما بيقول شي ما رح نروح عالسجن
If he doesn’t say anything, we won’t go to jail

It can be easy to overthink the conditional tense but the best way to improve your understanding is to begin to notice how native speakers are expressing conditional statements (for example, in the song Law by Elissa and Kona Momken Netefeq by Ramy Gamal). And remember that اذا is for optimists and لو is long gone :)