lök

lük is a derivational suffix in Turkic languages, most prominently Turkish, used to form abstract nouns that denote states, conditions, or qualities. The suffix is realized in four phonological allomorphs: -lık, -lik, -luk, and -lük. The choice among them follows phonological rules such as vowel harmony and the stem’s final sound, and all four forms are attested across Turkic languages.

Etymology and cognates: The suffix descends from Proto-Turkic *-lık and has cognates throughout the Turkic family. It is functionally equivalent to the English suffix -ness in indicating an abstract quality.

Usage and examples: It attaches to adjectives and some nouns to yield nouns naming a quality or state. Common examples in Turkish include temizlik (cleanliness) from temiz (clean); yalnızlık (loneliness) from yalnız (alone); güzellik (beauty) from güzel (beautiful); mutluluk (happiness) from mutlu (happy); bilgelik (wisdom) from bilge (wise).

In modern Turkish, -lık/-lik/-luk/-lük is a productive suffix used to expand the lexicon of abstract nouns in everyday language, literature, and education. The exact form used in a word is determined by phonology rather than semantic criteria. See also Turkish morphology, derivational suffixes, and the -lık family of suffixes.