In a manner that appears to require no physical or mental exertion; with ease and grace.
From 'effort' (from Old French 'esfort', meaning force or strength) combined with the negative suffix '-less' and the adverbial ending '-ly'. The concept emerged from the idea of achieving something without applying force or struggling against resistance.
Effortlessly is one of those paradoxical words that often describes the result of tremendous hidden effort - a master pianist plays effortlessly only after decades of practice, a swan glides effortlessly while paddling furiously underwater. It's the linguistic equivalent of making the difficult look easy.
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