contagiousness

WordReference Random House Learner's Dictionary of American English © 2025

con•ta•gious /kənˈteɪdʒəs/   adj. 

1. Pathology (of a disease) able to be spread by bodily contact with an infected person or object:
   contagious meningitis.
2. Pathology (of a person) carrying or spreading a contagious disease:
   Don't come near me; I'm still contagious.
3. tending to spread from person to person:
   contagious laughter.

con•ta•gious•ly, adv. 
con•ta•gious•ness, n. [uncountable]

WordReference Random House Unabridged Dictionary of American English © 2025

con•ta•gious  (kən tā′jəs), adj. 

1. Pathology capable of being transmitted by bodily contact with an infected person or object:
   contagious diseases.
2. Pathology carrying or spreading a contagious disease.
3. tending to spread from person to person:
   contagious laughter.

• Late Latin contāgiōsus, equivalent. to contāgi(ō) contagion + -ōsus -ous
• 1350–1400; Middle English

con•ta′gious•ly, adv. 
con•ta′gious•ness, con•ta•gi•os•i•ty  (kən tā′jē os′i tē), n.  Synonyms

• 1. Contagious, infectious are usually distinguished in technical medical use.
  Contagious, literally "communicable by contact,'' describes a very easily transmitted disease as influenza or the common cold.
  Infectious refers to a disease involving a microorganism that can be transmitted from one person to another only by a specific kind of contact; venereal diseases are usually infectious. In nontechnical senses,
  contagious emphasizes the rapidity with which something spreads:
  Contagious laughter ran through the hall.
  Infectious suggests the pleasantly irresistible quality of something:
  Her infectious good humor made her a popular guest.