indefatigably

IPA/ˌɪndɪˈfætɪɡəbli/
IPA/ˌɪndɪˈfætɪɡəbli/

indefatigably — adverb

1. in a way that shows steady determination and energy over a long period, without

1.adverbC2
Definition

in a way that shows steady determination and energy over a long period, without ever seeming to grow tired or want to stop

Example

Hiroshi worked indefatigably on the village water project for nearly three years.

modifies a sustained-effort verb (worked / campaigned / pursued)

The volunteers searched indefatigably through the rubble for survivors after the earthquake.

describes prolonged physical effort under hardship

Common collocations
  • worked indefatigably
  • campaigned indefatigably
  • fought indefatigably
  • searched indefatigably
  • indefatigably devoted
Synonyms
  • tirelessly

    everyday near-synonym; far more common in speech

  • untiringly

    literary; slightly more formal than tirelessly

  • relentlessly

    adds a sense of pressure or refusing to stop; can sound aggressive

  • doggedly

    emphasises stubbornness more than energy

Antonyms

Usage Note

Almost always modifies verbs that describe sustained, demanding work over weeks or years (campaigned, worked, fought, studied, searched). Rarely modifies short or one-off actions — saying someone 'jumped indefatigably' sounds odd because the activity is too brief.

Common Mistakes

She answered the question indefatigably.
She campaigned indefatigably for years.
the adverb needs an activity that lasts long enough to show tireless effort.
He ran indefatigably for ten minutes.
He trained indefatigably for the marathon.
the duration is too short for 'indefatigably' to fit naturally.

Word family

Synonym discussion

Sense: adverb/1

All five describe sustained effort without rest, but the texture differs. 'Tirelessly' is by far the most common in everyday Taiwanese-learner reading and feels warm and neutral — used freely in news and biography ('she works tirelessly for the poor'). 'Indefatigably' is its formal, literary cousin; it appears in obituaries, history writing, and political tributes, and sounds slightly old-fashioned in conversation. 'Untiringly' sits between them — more formal than 'tirelessly' but less ornate than 'indefatigably'. 'Relentlessly' shifts the focus from energy to refusal to stop, and often carries pressure or threat ('the police questioned her relentlessly'). 'Doggedly' highlights stubbornness through difficulty rather than physical energy ('he doggedly worked through every problem'). Use 'indefatigably' when writing admiringly about long-term campaigners or scholars; use 'tirelessly' in almost every other context.

indefatigably ↗tirelessly ↗untiringly ↗relentlesslydoggedly ↗

Common collocations

Phrases

  • worked indefatigably
  • campaigned indefatigably
  • fought indefatigably
  • searched indefatigably

Prepositions

  • indefatigably for (a cause)
  • indefatigably in (a role)

Etymology

LatinLate LatinEnglish

Adverb form of 'indefatigable', which English borrowed from Late Latin 'indefatigabilis' in the 16th century: 'in-' (not) + 'defatigare' (to tire out, from 'de-' down + 'fatigare' to weary). The adverbial '-ly' was added in English. The root sense is therefore 'in a way that cannot be wearied down', preserved almost intact in modern usage.