What does infirmity mean?
An infirmity is a condition of physical or mental weakness, especially one associated with illness or old age. In ordinary use, the word has a somewhat formal and often solemn tone, suggesting frailty rather than an ordinary, temporary complaint. It can also refer more broadly to a weakness or defect, such as a weakness in an institution or an argument. Historically and etymologically, infirmity is closely related to the idea of not being firm: the word comes from Latin infirmitas, formed from infirmus, meaning “not strong” or “weak.” Although the modern word is usually used for a person’s physical or mental condition, its older sense as a general weakness or imperfection is also attested. Infirmity is useful in formal writing when describing vulnerability, deterioration, or a fundamental limitation.
nounPhysical or mental weakness, especially the infirm condition associated with old age or illness. It can also refer to a weakness or defect in a person, institution, or system.
- Physical or mental weakness, especially in old age or illness.
- A weakness, defect, or limitation in a person, institution, or system.
"She continued to work despite the infirmity that had confined her to her home."
"The doctor said that age-related infirmity was affecting her mobility."
"The report examined the infirmity of the system that had allowed the error to go unnoticed."
Used when referring to multiple physical or mental infirmities, or to several weaknesses or defects.
"The policy was designed to address the infirmities of the existing system."
Infirmity literally means the absence of firmness: its roots link bodily weakness to the Latin for “not strong.”
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does infirmity come from?
Infirmity comes from Latin infirmitas, a noun meaning weakness or sickness, formed from infirmus, “not strong” or “weak.” The Latin adjective combines the negative prefix in- with firmus, “strong, firm,” a root also represented in English by firm, affirm, and confirm. Middle English borrowed the word in the sense of physical or mental weakness, and its use for the condition of old age or illness became especially prominent in the early modern period.
Related word forms
How infirmity is actually used
The word is formal and often conveys lasting weakness associated with illness or old age. In extended or figurative use, it can describe a serious structural weakness, though this usage is less common.
Easily confused with infirmity
Infirm is an adjective meaning physically or mentally weak, while an infirmity is the noun naming the condition or weakness itself.