Sumac

Many people have heard of "poison sumac" but the word sumac refers to different plants:

Sumac, also known as rhus, rhus coriaria: "is any one of about 35 species of flowering plants in the genus Rhus and related genera, in the family Anacardiaceae. The dried and powdered fruits of Rhus coriaria are used as a spice in Middle Eastern cuisine." [link] 

Poison Sumac, Toxicodendron vernix, is "is a woody shrub or small tree.  All parts of the plant contain a resin called urushiol that causes skin and mucous membrane irritation to humans. When the plant is burned, inhalation of the smoke may cause the rash to appear on the lining of the lungs, causing extreme pain and possibly fatal respiratory difficulty." [link]

Please be sure you don't confuse the two.

Further Reading

"Why You Should Be Adding Sumac to Your Cocktails" Food52 [link]