Definition of infectious in English:

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Pronunciation: /inˈfekSHəs/


1(Of a disease or disease-causing organism) likely to be transmitted to people, organisms, etc., through the environment.
Example sentences
  • However, conjunctivitis caused by the common cold is very infectious and can spread rapidly between people.
  • Severe acute respiratory syndrome is highly infectious and potentially lethal.
  • Glandular fever is an infectious illness that causes swelling of the lymph nodes.
1.1Likely to spread infection: the dogs may still be infectious
More example sentences
  • Dutch botanist Martinus Bijerinck called this infectious fluid contagium vivum fluidum.
  • She was misdiagnosed with gastro-enteritis, and transferred to Castle Hill because it was felt she was infectious.
  • By the way, colds spread through touching infectious surfaces or inhaling viruses.
1.2Likely to spread or influence others in a rapid manner: her enthusiasm is infectious
More example sentences
  • The problem is once you fall for the guy with the infectious laugh or the girl that takes your breath away, you have to get them to notice you.
  • He had a wonderful sense of humour and an infectious, hearty laugh.
  • It does make you an energetic person, and one who has an infectious and personable manner.
irresistible, compelling, persuasive, contagious, catching


On the differences in meaning between infectious and contagious, see contagious (usage).



Pronunciation: /inˈfekSHəslē/
Example sentences
  • At the same time, a European-derived painting style called Neo-Expressionism proved to be infectiously popular amongst the Art Institute students.
  • Though markedly different, both have strong elements of dance, which had the conductor almost pirouetting on the rostrum, thus coaxing infectiously springing rhythms from his colleagues.
  • Churchill's infectiously ebullient personality had served his government and his country well in the First World War as well as the Second.


Pronunciation: /inˈfekSHəsnəs/
Example sentences
  • An overwhelming majority of persons living with HIV infection do not get detected and remain unknowing of their potential illness and infectiousness to others.
  • If one takes these vibrios and cultivates them on nutritional media in the lab, or uses them to infect animal models, their infectiousness declines rapidly.
  • Perhaps this is why the film is best seen in a crowded theatre, where the infectiousness of cathartic emotion can have full play.

For editors and proofreaders

Syllabification: in·fec·tious

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