Derecho = straight. Ends with “o”.
Derecha = to the right. Ends with “a”
Easy to remember as to the left is “izquierda”. Ending with an “a”.
But there is the more definitive usage that is masculine or feminine. So sometimes it can end with an “o”, for the feminine usage.
Disclaimer - I do not speak Spanish.
Yhanks for explaining the subtle differences.
No, “o” for masculine (”honcho”), “a” for feminine (”senora”).
Other Spanish influence along this line shows up as for Philippines: “Filipino” and “Filipina”.
A mistake on my Filipina wife’s birth certificate has her first name ending with an “o” instead of the intended “a”. She no likey, but it’d be a bunch of trouble to change it, so she hasn’t.