Main Difference
The main difference between Aspen and Birch is that the Aspen is a common name for certain tree species and Birch is a genus of plants.
Aspen
Aspen is a common name for certain tree species; some, but not all, are classified by botanists in the section Populus, of the Populus genus.
Birch
A birch is a thin-leaved deciduous hardwood tree of the genus Betula (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus Betula contains 30 to 60 known taxa of which 11 are on the IUCN 2011 Green List of Threatened Species. They are a typically rather short-lived pioneer species widespread in the Northern Hemisphere, particularly in northern areas of temperate climates and in boreal climates.
Aspen (adjective)
Pertaining to the asp or aspen tree.
Aspen (adjective)
Tremulous, trembling.
Aspen (adjective)
Of a woman’s tongue: wagging, gossiping.
Aspen (noun)
The asp tree; a kind of poplar tree (genus noshow=1). A medium-size tree with thin, straight trunks of a greenish-white color.
“Above a certain elevation, the aspens gave way to scrubby, gnarled pines.”
Aspen (noun)
The wood of such a tree; usually pale, lightweight and soft.
“She claimed that aspen was the only “proper” material from which make a wicker basket.”
Birch (noun)
Any of various trees of the genus Betula, native to countries in the Northern Hemisphere.
Birch (noun)
A hard wood taken from the birch tree, typically used to make furniture.
Birch (noun)
A stick, rod or bundle of twigs made from birch wood, used for punishment.
Birch (noun)
A birch-bark canoe.
Birch (verb)
to punish with a stick, bundle of twigs, or rod made of birch wood.
Birch (verb)
to punish as though one were using a stick, bundle of twigs, or rod made of birch wood.