Definition of alnus
1 capitalized : a genus of alders (family Betulaceae) found in the north temperate zone and the Andes and having toothed leaves, a 4-parted calyx, and a woody conelike fruit
2 plural -s : any plant of the genus Alnus
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Origin and Etymology of alnus
New Latin, from Latin, alder — more at alder
First Known Use: 1733
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