This is only because spanish doesn’t like repeating “a” sounds like laagua would have since it can create ambiguity in the sentence. If agua was la agua the words would probably eventually end up smushed together making lagua instead.
Other romance languages have words that really change gender tho. I think Italian and Romanian do. Arguably they are neuter but have in singular masculine endings and in plural feminine or was it the other way around
This is only because spanish doesn’t like repeating “a” sounds like la agua would have since it can create ambiguity in the sentence. If agua was la agua the words would probably eventually end up smushed together making lagua instead.
Other romance languages have words that really change gender tho. I think Italian and Romanian do. Arguably they are neuter but have in singular masculine endings and in plural feminine or was it the other way around