The process or result of notching or indenting margins; a notch, indentation, or marginal indentation on a leaf, petal, or other structure.
From emarginate plus -tion (Latin -tio, denoting action or state). This noun form makes 'emargination' the standard term for describing the actual notch or the process creating it.
A 'heart-shaped' leaf's distinctive notch at the top? That's called an emargination—botanists have specific vocabulary for every tiny feature, so different species can be distinguished with absolute precision!
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