Cillin

Part of speech: noun

Definitions

1. A word element found in the names of penicillin-derived antibiotic drugs such as ampicillin and amoxicillin
2. The standard ending added to the names of antibiotics that share the penicillin chemical structure
3. A combining form used in pharmaceutical names to mark an antibiotic belonging to the penicillin family

Etymology: The "-cillin" ending is a pharmaceutical coinage, not an old word with a long history. It was built from "penicillin," the antibiotic discovered by Alexander Fleming in 1928 and developed into a usable drug in the early 1940s. Penicillin itself takes its name from "Penicillium," the mould genus that produces it, from Latin "penicillus," meaning "paintbrush" or "little tail," a reference to the brush-like shape of the mould's spore-bearing filaments under the microscope. Pharmacologists began splitting that name into a reusable element. Because the penicillins share a core chemical structure, the chemists who made new variants gave them names ending in "-cillin" so a clinician could recognise the family at a glance. Ampicillin, methicillin, amoxicillin and flucloxacillin all follow this pattern. The suffix works like a family surname: the shared ending signals a shared structure and mode of action, while the front part of each name distinguishes one drug from another.