Definition of "five-membered" []

• Of a chemical compound having a ring with five members (adjective)

WordNet. Princeton University. 2010.

• "The dark blue copper ion is bonded in a cavity between two imidazole groups (the five-membered rings) and two yellow sulphur atoms."
• "Some chemists were convinced the structure contained two five-membered rings connected by a single bond, known as a thiazolidine-oxazolone."
• "Others were equally sure it was a four-membered ring fused to a five-membered ring, known as a beta lactam."