noun

nonchalance

nahn-shuh-LAHNSS/ˌnɑːnʃəˈlɑːns/

A calm lack of concern or interest.

The woman reacts with nonchalance to the spill beside her tipped glass.

A middle-aged woman sits casually beside a small spill from her tipped water glass, leaning back with a loose, unconcerned shrug rather than rushing to clean it up.

Etymology

nonFrenchnot

+chalFrenchto have concern for

+anceFrenchstate or quality

French chaloir, 'have concern for,' ultimately comes from Latin calere, 'be hot.' Negating that concern gives nonchalance its sense of unconcern—the 'coolness' expressed by calm indifference.

In context

Justin Kwan3:49

it shows that effortless style a bit of nonchalance and a good Irish linen that is around 270 to 350 grams is actually quite substantial

3 Suit Fabrics Explained: Wool, Cotton & Linen | Beginner Suit Advice

More examples

His nonchalance about the deadline worries the rest of us.
I hide my excitement behind an air of nonchalance.
Despite her apparent nonchalance, she checks her phone every minute.

Forms

nonchalance

nonchalant adjective — Calm and seemingly unconcerned or uninterested.

nonchalantly adverb — In a calm, casually unconcerned manner.

Similar words

indifference: Suggests little interest or preference, without necessarily appearing relaxed.
unconcern: Emphasizes lack of worry rather than a casually relaxed manner.