Without end or limit; continuing on and on, or for a very long time.
From Old English 'endeleás' combining 'ende' (end) and 'leás' (without). The '-ly' adverb suffix transformed the adjective 'endless' into this modern form.
Philosophers have been arguing about whether anything is truly endless since ancient times, but what's wild is that infinity actually shows up in nature—fractals repeat endlessly at smaller and smaller scales, and electrons in atoms supposedly orbit endlessly. The word describes something mathematicians couldn't even properly define until the 1600s.
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