Fortitude is a formal word that refers to the strength of mind that enables someone to encounter danger or to bear pain or adversity with courage. Less formal words with similar meanings include grit, fiber, and pluck.

// To reach the summit of the mountain requires not only great physical strength and training but the fortitude to persevere no matter the challenge.

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“Managing is never a one-size-fits-all process. Personality, fortitude, and experience all matter, as does context.” — Gary Deer, The Daily Gazette (Xenia, Ohio), 28 Mar. 2026

Fortitude comes from the Latin word fortis, meaning “strong,” and in English it has always been used primarily to describe strength of mind. For a time, the word was also used to mean “physical strength”; William Shakespeare used it that way in Henry VI, Part 1: “Coward of France! How much he wrongs his fame / Despairing of his own arm’s fortitude.” But despite use by the famous bard, that meaning languished and is now considered obsolete. Even the familiar phrase “intestinal fortitude” is just a humorous way to refer to someone’s courage or mental stamina, not the literal strength of their digestive system. (If you’re looking to describe a mighty gastrointestinal tract, we might suggest “iron stomach.”)