infallible

"Fallible" means capable of making mistakes — or, easier to remember — capable of failing. Infallible means exactly the opposite — incapable of failing.

This word is often used to describe human capacity for error — no one is infallible. And yet, we are able to be infallible in certain ways: children are infallibly curious, teenagers infallibly hungry. Interestingly, infallible derives from the Latin in- "not" + fallere "deceive." When did making a mistake and deception become the same thing?

Definitions of infallible
1

adj incapable of failure or error

“an infallible antidote”
“an infallible memory”
“the Catholic Church considers the Pope infallible
“no doctor is infallible
Synonyms:
foolproof, unfailing
not liable to failure
inerrable, inerrant, unerring
not liable to error
Antonyms:
fallible
likely to fail or make errors
errant
straying from the right course or from accepted standards
erring, error-prone
capable of making an error
undependable, unreliable
liable to be erroneous or misleading
weak
likely to fail under stress or pressure
show more antonyms...

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