Infectious

How to spell infectious

10 letters · 3 syllables

How to pronounce infectious

Say the part in capitals loudest.

What does infectious mean?

1. adjectiveCapable of being spread, especially of a disease passed from one person to another, or of a mood or quality that others readily catch.

Infectious in a sentence

• The doctor warned that the virus is highly infectious in its early stages.

• Her infectious enthusiasm soon spread around the whole office.

Where does infectious come from?

Language of origin: Latin

This word traces back to the Latin verb inficere, which literally meant 'to put in' or 'to dip into', formed from the prefix in- ('into') and facere ('to make or do'). In Latin the sense soon shifted toward 'to taint, stain or spoil', because dipping something into a dye or poison changed its nature. From the past participle infectus came the medieval Latin infectiosus, and English adopted 'infectious' in the early 1500s to describe diseases capable of spreading from one body to another. The same facere root, which means 'to make', also sits inside familiar relatives such as 'affect', 'perfect' and 'factory', which explains the slightly hidden 'fect' in the middle of the word. By the 1600s the meaning had broadened to anything readily caught or shared, such as an infectious laugh, while the spelling keeps the tell-tale -tious ending that sounds like a simple 'shus'.

How the word is built

• in- (into)
• fect (from facere: to make/do)
• -ious (adjective suffix)