What does antibiotics mean?
Antibiotics are medicines designed to combat bacterial infections by killing bacteria outright or preventing them from multiplying. Since Alexander Fleming's discovery of penicillin in 1928, they have transformed medicine, turning once-fatal conditions such as pneumonia, sepsis, and simple wound infections into treatable illnesses. In everyday English, 'antibiotics' is always plural: patients take 'a course of antibiotics', and doctors may 'prescribe antibiotics' for conditions like strep throat or urinary tract infections. Crucially, they work only against bacteria — not viruses — so they are ineffective against colds and flu. The word now carries a note of caution in public discourse, since overuse has driven the rise of antibiotic-resistant 'superbugs', making responsible use a major global health priority. Few words in modern vocabulary carry such a dramatic story of scientific triumph and ongoing challenge.
nounMedicines that kill bacteria or inhibit their growth, used to treat bacterial infections. The term is almost always used as a plural mass noun referring to the class of such drugs collectively.
- Substances derived from microorganisms or produced synthetically that destroy or inhibit the growth of bacteria, used to treat bacterial infections.
"The doctor prescribed a course of antibiotics to clear up the infection."
"She finished her course of antibiotics and made a full recovery within a week."
"The overuse of antibiotics in livestock farming has been linked to rising rates of drug-resistant bacteria."
The word functions as a plural-only noun in common usage; it takes plural verbs ('antibiotics are effective'). To refer to one drug, use 'an antibiotic'.
"Antibiotics are ineffective against viral illnesses such as the common cold."
Penicillin, the first antibiotic, was discovered by accident in 1928 when Alexander Fleming noticed mould killing bacteria in a petri dish he had left out while on holiday.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does antibiotics come from?
The term derives from the Greek 'anti-' meaning 'against' and 'bios' meaning 'life', combined into 'antibiosis', first used in the late 19th century to describe organisms that harm one another. The adjective 'antibiotic' was applied to these bacteria-killing substances following Fleming's discovery of penicillin, and the plural noun form became standard medical vocabulary by the mid-20th century. It shares its Greek roots with words such as 'biology', 'symbiosis', and 'biotic'.
Related word forms
How antibiotics is actually used
Always treated as a plural noun in English — one speaks of 'antibiotics are', never 'an antibiotics is'. A single drug is referred to as 'an antibiotic'. The word carries strong modern connotations of medical caution due to growing awareness of antibiotic resistance.
Easily confused with antibiotics
Antibiotics are drugs that kill or inhibit bacteria, while antibodies are proteins produced by the immune system to neutralize pathogens.
'Antibiotic' can function as an adjective or refer to a single such drug, whereas 'antibiotics' refers to the class of drugs collectively.