Heard spelling

gynoesium

Spelled gynoecium. a soft c

Should it be gynoesium?

No. The letter is c, and it sounds like s only because an i follows it.

Latin softens a c in front of e, i and y, so cium and sium are one sound and two histories. This c comes from the k of oikos, hardened by Latin into a c and then softened again by the vowel behind it. Writing s spells the present and erases the route.

Say

guy-NEE-see-um, and jy-NEE-see-um is heard just as often

Letters

G-Y-N-O-E-C-I-U-M