There are about 200 different terpenes that have been identified in the cannabis plant.  That said, terpenes are not exclusive to the cannabis plant but they can also be found in several other plants and flowers.
Terpenes provide the unique aromas that we often associate with the different cannabis strains. For example, strains with high myrcene content will have an earthy aroma while those with high limonene content are likely to have a strong citrus aroma.
Cannabis-derived terpenes are extracted from the cannabis plant while non-cannabis-derived terpenes are derived from different plants and flowers, other than cannabis. Non-cannabis-derived terpenes can be natural (botanical) or synthetic (manufactured synthetically in the lab).
Cannabinoids are the major bioactive molecules in cannabis and they have shown significant therapeutic potential. Even though terpenes have demonstrated therapeutic potential , research has also shown that they enhance the healing properties of cannabinoids through the entourage mechanism.  However, some manufacturers prefer to produce cannabidiol (CBD) and tetrahydrocannabinol (THC) isolates in a pure form, without the presence of terpenes and other cannabis constituents. Do cannabis-derived terpenes have value as isolates and how are they being used after their extraction?
A number of cannabis producers are putting cannabis-derived terpenes to good use even if they are 20 times more expensive than terpenes extracted from other sources. According to the sales and marketing president of a Texas cannabis company, extracting terpenes from cannabis is cost-prohibitive and they could be extracted from other plants containing the same desired compound in higher concentrations such as the molecule limonene contained in cannabis but also in citrus fruits.
Cannabis-derived terpenes have both advantages and disadvantages. On the good side, they are able to replicate the unique aromas of different cannabis strains and they can provide a beneficial entourage effect. On the flip side, they are costly to produce, given the cost of the plant biomass, extraction machineries, solvents, etc. It should be noticed that Cannabis-derived terpenes are illegal in states that are yet to legalize cannabis.
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 Sommano, S. R. et al. The Cannabis Terpenes. Molecules (2020); 25(24), 5792. Journal [Impact Factor= 4.411] [Times Cited=12]
 Ferber, S. G. et al. The “Entourage Effect”: Terpenes Coupled with Cannabinoids for the Treatment of Mood Disorders and Anxiety Disorders. Current Neuropharmacology (2020); 18(2), 87–96. [Journal Impact Factor= 7.24] [Times Cited= 29]