adjective
infectious
ihn-FEHK-shuhs
adjective
1
Able to be passed from one person or animal to another, usually through germs.
"Chickenpox is highly infectious among young children."
"Patients with infectious diseases were kept in isolation."
2
Quickly spreading to affect other people's mood or behaviour.
"Her infectious laugh had the whole room smiling."
How to Use Infectious
Learner’s notesIn plain EnglishEasily spread from one person to another — either a germ, or a mood like enthusiasm or laughter.
Common mistake
Often confused with contagious: contagious usually means spread by direct contact, while infectious covers a broader range of transmission routes and, informally, moods too.
Easily confused with
Common pairings
infectious disease
infectious enthusiasm
highly infectious
Word Forms
more infectious comparative, most infectious superlative
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Chickenpox is highly _____ among young children.
Etymology
From New Latin īnfectiōsus, from infect + -ious.