黏 (nián, sticky) and 粘 (zhān, to stick/paste) are often confused. 黏 describes the quality of being sticky, while 粘 is the action of sticking something. However, in practice they are often used interchangeably.
Left 黍 is broomcorn millet, a sticky-grained cereal central to north-China cuisine - its very name evoked the gummy texture that gave rise to words for stickiness. As the indexing radical it puts 黏 firmly in the sticky-grain family (糯 glutinous rice, 粘 to glue) and gives the whole semantic load: anything tacky like millet paste.
Right 占 supplies the sound zhān → nián through a familiar zh/n alternation in this phonetic series (also seen in 粘 zhān/nián, 沾). The same right-side phonetic appears in 站 stand, 战 fight, 点 dot - knowing 占 unlocks the readings of all of them.
