昆 is a bound morpheme that appears mainly in proper names and classical literary terms. It serves as the first element of 昆仑 (Kūnlún, the Kunlun Mountains) and 昆明 (Kūnmíng, the capital of Yunnan). In classical Chinese culture, it also refers to 昆曲 (Kūnqǔ), a form of opera, and 昆体 (Kūntǐ), a formal style of poetry. You won't encounter 昆 alone in modern speech—it's always part of a larger word.