Easily-confused!
If your specimen is:and has stems/​leaves ar­ranged:and the leaves have/are:and the bark is/has:and the twigs:and the fruit (if present):then you have:
no more than waist-high (<1 m) (<3 ft) ╟ alternate ▲▲ teeth no hair lookalike alderleaf buckthorn  Rhamnus alnifolia.
a tree ▲▲ 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.
___ smooth margins or
▴▴▴▴ very small teeth (use 🔎︎ hand-lens)
dark, lots of light-colored lenticels no terminal thorn;
hairy
this plant, please continue below …
___ smooth margins,
taper at both ends, and
pass the dogwood leaf test
no con­spic­u­ous lenticels nor strong colors lookalike 2 species of dogwood  genus Cornus.
sub-opposite ▴▴▴ small teeth (can use 👀︎ naked eyes) 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.
╫ opposite ___ smooth margins,
taper at both ends, and
pass the dogwood leaf test
no con­spic­u­ous lenticels nor strong colors lookalike all-but-2 species of dogwood  genus Cornus.

Verify with 🔍︎ images.

Learn more about glossy buckthorn Frangula alnus

Treatment methods and timing (40-45°N lat.)  Adobe Acrobat Reader file Management and Control (Wisconsin)  Adobe Acrobat Reader file Best Control Practices BCP (Michigan)  Adobe Acrobat Reader file
Native alternatives (Great Lakes green entries)  Adobe Acrobat Reader file (page 4) Native alternatives (Missouri Botanical Garden).

🔍︎ 🔍︎ images Discover Life Encyclopedia of Life Michigan Flora Minnesota Wildflowers Flora of North America NRCS PLANTS db USFS Wikipedia