Main Entry: ul·tra·struc·ture

Pronunciation: \ˈəl-trə-ˌstrək-chər\

Function: noun

Date: 1939

: biological structure and especially fine structure (as of a cell) not visible through an ordinary microscope

— ul·tra·struc·tur·al \ˌəl-trə-ˈstrək-chə-rəl, -ˈstrək-shrəl\ adjective

— ul·tra·struc·tur·al·ly adverb