I read the help sections on aliases and implications, and as I understand it, the tag "sole_male" is always aliased (replaced by) "male" whenever you search with it. The auto-suggest shows this. I don't think this is a good idea. This sounds like it should be an implication, where sole_male should imply male, not be aliased with it. Aliasing them restricts searchability. As far as I can tell, there's no way to search for posts by the number of gendered participants. The tag for group works, but there doesn't seem to be a way to specify that you want a single female and a bunch of males or a single male and a bunch of females, etc. Many other booru style sites have this option. I didn't consider this a suggestion for an alias or implication, as it's questioning what was probably a very early use of this feature.

See topic #26274 for the discussion on why solo_male got aliased to male.

topic #26274: Why is male/solo aliased to male?
topic #26153: Why has the Solo_(insert gender) tags disappeared?
topic #23175: What happend to the solo_male and solo_female tags?
topic #21901: Gender tags
topic #20565: solo_male tag
topic #18716: Solo males
topic #12591: Solo_Gender tags
topic #11215: Tag Alias: solo_female -> solo
topic #5312: Male Solo/Female Solo tag?
topic #817: Tag Alias: solo_male -> invalid_tag

the transgender hivemind really put a huge feminine penis in e621 tags