What does fatigue mean?
Fatigue denotes profound physical or mental weariness brought on by exertion, illness, or sustained stress — a state heavier than ordinary tiredness and one that resists a single night's rest. It is also the standard term in engineering for the progressive weakening of materials, especially metals, under repeated stress, which is why engineers speak of 'metal fatigue' when a component fails after countless load cycles. In medicine it appears in conditions such as chronic fatigue syndrome, lending it clinical seriousness, while phrases like 'compassion fatigue' extend it metaphorically to emotional burnout. Borrowed into English from French in the seventeenth century, the word ultimately traces to Latin 'fatigare', to weary. Its connotations are almost invariably negative, signalling depletion rather than restfulness, yet its range — human, emotional, and mechanical — makes it a versatile and precise word across medicine, engineering, and daily life.
Extreme tiredness or weariness, typically resulting from physical exertion, mental strain, illness, or lack of rest; also, in engineering, the weakening of a material under repeated stress.
"Driver fatigue is a leading cause of motorway accidents."
Plural 'fatigues' occurs mainly in technical contexts (e.g. multiple instances of material fatigue) or in the dated military sense of fatigue-duty garments.
To cause to become tired or weary; to weaken a material through repeated stress.
"Hours of cross-examination had visibly fatigued the witness."
The verb form survives mainly in technical and formal writing; everyday speech prefers 'tire out' or 'wear out'.
The plural is uncommon outside engineering ('fatigue failures') and the dated US military sense, where 'fatigues' refers to soldiers' work uniforms or assigned labour duties.
"He reported two separate fatigues in the wing structure during inspection."
Engineers fear fatigue as much as doctors do — in materials science, metal 'fatigue' describes how repeated stress quietly breaks steel and aluminium long before their rated limits.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of fatigue
Fatigue entered English in the early seventeenth century from French 'fatiguer', itself taken directly from the Latin verb 'fatigare', meaning to weary or tire out. The Latin root also yielded 'indefatigable', describing someone incapable of being worn down. A further connection to Latin 'fatum' (fate) has been suggested but remains uncertain.
How fatigue is actually used
In everyday speech 'fatigue' suggests a deeper, more persistent weariness than simple tiredness, and it carries clinical weight in phrases like chronic fatigue syndrome. The verb form is now largely confined to technical writing; the military sense of 'fatigue' as assigned chores is chiefly American and somewhat dated.