infectious
ihn-FEHK-shuhs
Infectious (adjective) means Able to be passed from one person or animal to another, usually through germs. Example: “Chickenpox is highly infectious among young children.”
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."
"Wash your hands often, because the cold virus is highly infectious."
2
Quickly spreading to affect other people's mood or behaviour.
"Her infectious laugh had the whole room smiling."
"His infectious enthusiasm made even the dull task seem fun."
"The band's infectious rhythm soon had everyone dancing."
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
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Word forms
- Comparative
- more infectious
- Superlative
- most infectious
Fill the gap
Can you complete this real example?
Chickenpox is highly _____ among young children.
Etymology
From New Latin īnfectiōsus, from infect + -ious.
Synonyms
View more →Antonyms
non-infectious
noninfectious
Related words
Rhymes for infectious
See all rhymes for infectious →Frequently asked questions
What does “infectious” mean?
The word “infectious” means able to be passed from one person or animal to another, usually through germs. In plain terms, easily spread from one person to another — either a germ, or a mood like enthusiasm or laughter.
How do you pronounce “infectious”?
“Infectious” is pronounced ihn-FEHK-shuhs (/ɪnˈfɛk.ʃəs/ in IPA).
How do you use “infectious” in a sentence?
Here is “infectious” used in a sentence: “Chickenpox is highly infectious among young children.”
What is the opposite of “infectious”?
The opposite of “infectious” — its antonyms — are non-infectious and noninfectious.
What part of speech is “infectious”?
“Infectious” is an adjective.
Where does the word “infectious” come from?
The word “infectious” comes from New Latin. From New Latin īnfectiōsus, from infect + -ious.
Is “infectious” a common word?
“Infectious” is a fairly common word in modern English, usually learned at around the B2 level.
How many meanings does “infectious” have?
“Infectious” has 2 distinct senses listed in this dictionary. The most common is: able to be passed from one person or animal to another, usually through germs.
What is the difference between infectious and contagious?
Infectious describes something able to be passed from one person or animal to another, usually through germs, and is often used for diseases spread by any means, including air, water, or vectors. Contagious more narrowly implies spread through direct contact, though the two words are frequently used interchangeably in everyday speech.
Can infectious describe something other than disease?
Yes, infectious can describe moods or behaviours that quickly spread to affect other people, such as 'infectious enthusiasm' or 'infectious laughter,' where the sense is figurative rather than medical.
What is the difference between infectious and infected?
Infectious describes the capacity to spread germs to others, while infected describes a person or organism that already has germs within them. Someone can be infected without necessarily being infectious to others, and vice versa depending on the stage of illness.
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