subspecialty

[ suhb-spesh-uh l-tee, suhb-spesh- ]
/ sʌbˈspɛʃ əl ti, ˈsʌbˌspɛʃ- /

noun, plural sub·spe·cial·ties.

a lesser or minor specialty: a cinematographer with a subspecialty of portrait photography.

Origin of subspecialty

First recorded in 1925–30; sub- + specialty