indefatigable
UK[ˌɪndɪˈfætɪɡəbl̩]US[ˌɪndɪˈfætɪɡəbl̩]
adj
(of a person or their efforts) persisting tirelessly; never showing signs of getting tired.
Morpheme Breakdown
in
de
fatigable
in
not
de
completely
fatigable
able to be tired
Etymology
The word "indefatigable" is a direct borrowing from the 16th century French indéfatigable, which itself was built from Latin components. Its core logic is a double negation: the Latin prefix in- ("not") negates the adjective defatigabilis ("able to be completely wearied"), which is formed from de- ("utterly") and fatigare ("to tire"). The literal sense is thus "not able to be utterly tired out." While the Latin verb fatigare is of uncertain deeper origin, possibly related to a lost Italic root, the word's construction perfectly captures its modern meaning of tireless persistence, describing someone whose capacity for effort seems incapable of being exhausted.
Analysis
Structure: in (not) + de (completely) + fatigable (able to be tired)
- in: Latin origin, a prefix meaning "not".
- de: Latin origin, a prefix used here as an intensifier meaning "utterly, completely".
- fatigable: From Latin fatigabilis (that can be wearied), from fatigare (to tire). The English form retains the spelling 'fatig' (to tire) + 'able' (capable of being).
Examples
She was an indefatigable campaigner for human rights.
His indefatigable energy inspired the whole team.
Through years of indefatigable research, she finally made a breakthrough.