Which aromatic resin is obtained from trees of the genus Boswellia?

Frankincense is an aromatic resin used in incense and perfumes, obtained from trees of the genus Boswellia in the family Burseraceae, particularly Boswellia sacra (syn. B. bhaw-dajiana), B. carterii, B. frereana, B. serrata (B. thurifera, Indian frankincense), and B. papyrifera. The word is from Old French franc encens ("high-quality incense").

There are five main species of Boswellia that produce true frankincense. Resin from each of the five is available in various grades, which depend on the time of harvesting. The resin is hand-sorted for quality.

The English word frankincense derives from the Old French expression franc encens, meaning "high-quality incense". The word franc in Old French meant "noble" or "pure".

A popular folk etymology suggests a connection with the Franks (and often in particular Frankish Crusaders), who reintroduced the spice to Western Europe during the Middle Ages, but the word itself comes from the expression.