Contagious means spreading easily from person to person. A contagious illness, highly contagious, contagious laughter.
Strictly, contagious means spread by contact and infectious means spread by any route including air, though the two are used interchangeably in ordinary speech. The figurative use is warm and common: contagious enthusiasm, contagious laughter. Note contagion, which means both the spreading and the disease; and that in finance, contagion is the standard word for a crisis spreading from one market to another.
1adjectivecontagiousSpreading easily from person to person.
“It is contagious for about two days before any symptoms show.”
synonyms: infectious, catching
2adjectivemoodSpreading easily, of a mood.
“Her laughter was so contagious that soon the whole class was giggling.”
contagious is a quality of spreading.
Also accepted in games: infectious
Latin contagiosus comes from contingere, to touch — con- plus tangere. Contact, contagion and contingent are the same verb, and a contagious disease is literally one caught by touching.
Latin
contagiosus
Old French
contagieus
English, today
contagious
From Old French contagieus, from Latin contagiosus, from contagio.
Etymology from Wiktionary, CC BY-SA
Practised in Body & Health