contagious

Definitions

con- (together) + tag- (touch) + -ous = "spreading by touching together." The original image is a disease that leaps the instant two bodies touch. English then handed it to anything that passes person to person — a contagious laugh, contagious panic.

Why It Means This

The figurative use is the interesting part. Once "contagious" stopped being only about germs, it became the perfect word for anything that jumps from person to person without anyone deciding to pass it on — laughter, yawns, panic, enthusiasm. The metaphor keeps the disease logic: you "catch" it just by being near someone who has it.

Common Collocations

• 1.highly contagious高度传染性
• 2.contagious disease传染病
• 3.contagious laugh会传染的笑声
• 4.contagious enthusiasm有感染力的热情

Example Sentences

• 1.

  Measles is highly contagious and spreads through the air.

• 2.

  Her enthusiasm was contagious, and soon everyone joined in.

• 3.

  Yawning seems to be contagious in a quiet room.

Easily Confused

contagious vs infectious — both describe spreading disease. contagious stresses spread by touch or close contact (a contagious skin disease). infectious stresses spread by a pathogen, including through air or water (an infectious virus). In the figurative sense both work (contagious/infectious laughter), but contagious is the more common choice.