hydrocarbon

ring; hoop; loop; (chain) link; classifier for scores in archery etc.; to surround; to encircle; to hem in

environment; circumstances; surroundings; ambient

(zoology) segment (of the body of a worm, centipede etc.); (fig.) a part of an integrated whole: aspect (of a project), element (of a policy), sector (of the economy), stage (of a process) etc.

to cycle; to circulate; circle; loop

alkane

aromatic hydrocarbon

(chemistry) alkyne