thylakos

Thylakos is a term of Greek origin meaning “sack” or “pouch.” In scientific language, it serves as a root used to name sac-like structures. The most widely recognized usage is in the word thylakoid, which refers to the membrane-bound sacs inside chloroplasts and cyanobacteria that participate in photosynthesis. Thylakoids are typically arranged in stacks called grana, connected by lamellae, and their membranes host the light-harvesting complexes, the electron transport chain, and ATP synthase.

The etymology traces to Greek thylakos, “sack,” combined with a suffix meaning “form” or “resembling,” producing terms that denote a sac-shaped or pouch-like structure. In anatomy and botany, the root appears in other terms describing vesicle- or sac-like features, though thylakos as a standalone term is rarely used outside of compound forms.

In modern biology, the concept associated with thylakos emphasizes subcellular architecture and function. The term’s usage highlights how ancient Greek roots continue to shape the nomenclature of cellular components.

Related terms include thylakoid and granum, which describe the sac-like organelles and their stacked arrangement within chloroplasts.