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A reader asks about the words fatigable, defatigable, and indefatigable:

Indefatigable apparently is of the same/identical meaning [as defatigable]. Then why is the ‘in’ used as a prefix of defatigable, when ‘in’ is generally used to invert the meaning, as in ‘incorrigible’ (antonym of corrigible)?

The reader says that he understands fatigable to refer to a person “who can be fatigued” and defatigable to a person “who can be treated for exhaustion.”

The reader has misunderstood the meaning of de- in indefatigable.

Note: The pronunciation of indefatigable is IN-duh-FAT-i-guh-buhl.

Fatigable and defatigable mean the same thing. They have Latin equivalents:

fatigare verb: to weary, tire, fatigue.
fatigatio noun: weariness, fatigue.

defatigare verb: to weary, fatigue, tire.
defatigatio noun: exhaustion, weariness, fatigue.

The Latin prefix de- is used with more than one meaning. One of these meanings, in both Latin and in English, is this:

de- (prefix): down to the bottom, completely, thoroughly.

Both fatigable and defatigable connote weariness, but the weariness expressed by defatigable is total exhaustion.

Latin also has source words for the form indefatigable:

indefatigabilis adjective: untiring
indefatigatus adjective: not tired

A Google search produces about 22,000 results for defatigable, 114,000 for fatigable, and 708,000 for indefatigable. The Ngram Viewer shows a marked decline in the use of indefatigable in recent decades.

Here are recent examples of the use of indefatigable on the Web:

Indefatigable drive and charisma have made Maura Healey the state’s attorney general and the one to watch in Massachusetts politics. 

To some, millennials— those urban-dwelling, ride-sharing indefatigable social networkers—are engaged, upbeat and open to change. To others, they are narcissistic, lazy and self-centered.

The marigolds are indefatigable. The geraniums are lush and valiant. 

The indefatigable Vermont Sen. Bernie Sanders, of course, led the pack.

Indefatigable is the opposite of defatigable and means, “incapable of being fatigued.”

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4 thoughts on “Indefatigable”

  1. Muddying the Google numbers on this is the HMS Indefatigable, She was the battlecruiser that lead the ‘charge’ on the Kaiser’s High Seas Fleet at Jutland. The Indefatigable took a direct hit that exploded her magazine. She went down so quickly that only two of her crew survived. It was similar to the sinking of the HMS Hood in World War II. HMS Indefatigable was the first casualty of the Battle of Jutland.

    Many books and articles have been written about the battle and the flaws in the battlecruiser’s design.

  2. Why would it be that I’ve spent my whole 66 years of life hearing this with the ‘g’ coming before the ‘t’? ‘Indefagitable’ … That’s how I would have spelled it.

    Maybe I’ll encounter an explanation in Steven Pinker’s _The Language Instinct._ I just got it the other day (no, not that day, the other day). I’m about halfway through; had to get another of his after reading _The Stuff of Thought_ a few years ago. Enlightening.

  3. “Note: The pronunciation of indefatigable is IN-duh-FAT-i-guh-buhl.” Bless you!

    The reader also makes a mistake of degree by assuming that the prefix “in” denotes oppositeness. Like “de”, “in” has multiple meanings including being an intensifier or enactor (there). Hence, the famous example of inflammable which, perfectly logically, means capable of being “inflamed”. Inflamed, obviously meaning to become flaming. In most English words this “in” meaning has been replaced by “en”. But not in all. Here was a case where public safety supposedly demanded bad language and we now have the artificial “flammable” as the common warning in print. A shame, because it is hard to think of a better incentive for learning what words actuallymean, instead of what it “seems” like they mean than insisting on inflammable’s proper application. I guess there are innocent bystanders to consider.

    @Curtis Manges: Goo god, I don’t know. Have you also always said “faggited” or “faggit” when meaning fatigue(ed)? Did you never make that connection?

  4. Thank you, Mister Furkles, for the history on the battlecruiser. When my son saw what we were reading about today (we read this blog daily but are a few weeks behind) he said, “Oh, that ship” and then he wanted to know if it was sunk. We watched the Horatio Hornblower series several years ago, but honestly, mom only half-watches some things so I could not remember if it sunk or not. It took me long enough to master the pronunciation of the word with fluency.

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