is a 副詞（ふくし） (adverb) in Japanese that strengthens the base meaning of もし
‘a bit’. Therefore, the literal meaning of もしも
is ‘even a bit’. Despite this, as もし
are almost exclusively paired with sentences that use some sort of 仮定（かてい） ‘assumption’, or ‘hypothesis’ based expression, もしも
will often be translated as ‘supposing that’.
will be used at the beginning of sentences that include almost any form of 仮定（かてい） expression. For example, ば
, or ても.
Supposing that you move within this year, I will help you.
Supposing that you get hurt at work, the site will be shut down, so please be careful.
Assuming you have a day off tomorrow, do you want to go to the museum with me?
Supposing he even were here, don't you think we would not have been able to complete it by today?
is considered a stand-alone adverb, it is just a combination of もし
, and the 副助詞（ふくじょし） (adverbial particle) も.
are most often used to express some type of result. This means that (B) will happen if (A) happens, or if (A) is true. However, たとえ is contrastive, and therefore asks ‘what the result’ of a specific situation may be.
Assuming you forget your homework again, I will call your parents. (Calling their parents will be the result of forgetting their homework)
If, for example, the test is hard, don't give up, and do your best until the very end. (If the test is difficult, doing your best is not a result, just one of many choices that could be made)