Not causing any damage, injury, or danger; completely safe.
From Old English 'harm' combined with the suffix '-less' meaning without. 'Harm' comes from Proto-Germanic and has roots meaning 'hurt' or 'damage'.
The word 'harmless' is more complex than it seems—something can be personally harmless but ecologically devastating, like an invasive species, showing that 'safe' depends entirely on perspective and context.
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