Having the shape or pattern of waves; moving up and down in a smooth, flowing motion like water waves.
From the noun 'wave' (Old English 'wafian,' to wave or undulate) plus the suffix '-y' (full of, having the quality of). The adjective form developed naturally to describe anything with wave-like properties.
Water waves and sound waves and light waves all use the word 'wave,' but they're completely different phenomena—what connects them is the mathematical shape they make, which physicists call the sine function.
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