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How to spell infectious

Infectious is spelled I-N-F-E-C-T-I-O-U-S.

hear itin·fec·tious/ɪn'fɛkʃəs/adjectiveSchwa and roots

What it means: Easily spread to others.

In a sentence: The doctor's laugh was so infectious that everyone started giggling.

The part people get wrong

Watch for an unstressed vowel that is hard to hear.

Same family: infection, infected, infective, infectiousness, infectious disease. If you can spell one, the shared part carries to the others.

Where it comes from: “Infectious” comes from the Latin verb *infectus*, past participle of *inficere*, meaning “to stain, taint, or corrupt.” Over time, English shifted the idea from “tainting” to the modern sense of spreading disease—or even spreading emotions like laughter.

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