Board Thread:Magnus Chase & the Gods of Asgard/@comment-24098124-20180726234609/@comment-33461874-20180921201604

Bigender often can mean that you fluctuate between two distinct personas, each having different genders. For example, someone who is has a male personality sometimes, and a female personality other times. Genderfluid means that only your gender will change, but your personality more or less stays the same (your personality may change to be somewhat less jumpy and happy if you're suffering through gender dysphoria, but that's a whole different thing altogether that I won't even try to get into, as I don't want this to end up more of a tangent).

Also, bigender focuses more on the extreme ends of the gender spectrum, usually varying from heavily masculine to heavily feminine. Genderfluidity implies that at some points, you are in between, and located on a part of the gender spectrum that is in the middle of male and female.

On top of this, the way that genderfluid is defined officially is as, "a person who ... prefers to remain flexible about their gender identity rather than committing to a single gender," whereas bigender people often are against the fluctuation and wish for it not to happen (actually, the terminology for that is alternating gender incongruity, or AGI). Due to this, Alex is most likely genderfluid, because, 1) although they haven't been described as being somewhere in between male and female in the books, they could have been a some point that we simply don't know of, and 2) they seem pretty okay with being genderfluid.

And just as PoseidonEpicness45 said... they said they were genderfluid, so they are!