Here is a list of nouns that start with SO.

soaking, soap, sobriety, sobriquet, soccer

sociability, social, socialism, socialist, sociality

socialization, society, sociologist, sociology, sock

socket, sod, soda, sodium, sofa

softener, softening, softwood, soil, sojourn

sojourner, solace, solder, soldier, soldiery

sole, solemnity, solenoid, solicitor, solicitude

solid, solidarity, solidity, solipsism, solitary

solitude, solo, soloist, solstice, solution

solvency, solvent, soma, someplace, somersault

somewhere, sommelier, somnolence, son, sonar

sonata, song, songbook, sonnet, sonny

sonofabitch, sonogram, sonority, soot, sop

sophisticate, sophistication, sophomore, soprano, sorghum

sorority, sorption, sorrel, sorrow, sort

sortie, soubriquet, souffle, soul, sound

soup, source, sourdough, soutane, southpaw

souvenir, sovereign, sovereignty, soviet, sowbelly

sowing, soy, soybean

Hope you enjoy this page of nouns that start with so and the rest of this noun list a-z site as well.