If we’re just talking math, triangles can be defined in terms of 3-element subsets of all 3 (A)ngles and 3 (S)ides:
SSS - unique
SAS - unique
ASS - may be unique depending on the lengths of the sides
ASA - unique
SAA - unique
AAA - infinite solutions

Maybe someone cleverer than me can figure out how that maps on to love and gender.