If your specimen is a:and has stem/​leaf ar­range­ment:and the leaves have/are:and the bark is/has:and the twigs:and the fruit (if present):then you have:
tree╫ opposite (most species) — smooth,
taper at both ends, and
pass the dogwood leaf test
no con­spic­u­ous lenticels nor strong colors lookalike dogwood  genus Cornus
sub-opposite small ▲▲ teeth dark, lots of light-colored lenticels

inner bark=orange (scrape with knife)
often have a terminal thorn are small, black, taste disgusting after a few seconds — spit it out lookalike common buckthorn  Rhamnus cathartica
╟ alternate — smooth or
very small ▲▲ teeth (use 🔎︎ hand-lens)
dark, lots of light-colored lenticels no terminal thorn ;
lookalike glossy buckthorn  Frangula alnus
▲▲ teeth, visible within arm's length dark, lots of light-colored lenticels

if mature, looks covered with burnt potato chips/crisps
are small, black, taste like 🍒︎ cherry even if sour lookalike 🍒︎ black cherry  Prunus serotina
no more than waist-high (<1 m) (<3 ft)▲▲ teeth no hair this plant, please continue below …

Verify with Google images.

Also called alder buckthorn (although do not confuse with glossy buckthorn  Frangula alnus which is also called that).

Native to North America.

Uses by native peoples
(Ethnobotany database)

Learn more about alderleaf buckthorn Rhamnus alnifolia

Discover Life Encyclopedia of Life Google Google images Michigan Flora USDA PLANTS db Wikipedia