TAC

What Is TAC?
TAC, in weed terminology, refers to total active cannabinoids—the amount of detectable cannabinoids in a cannabis product that will, in some way, affect its high or overall effects. This synergistic relationship is known as the entourage effect. Sometimes expressed in the context of TAC vs THC, the two are not in opposition, but rather enhance each other.

The entourage effect is currently little-understood, to the extent that its existence is not even certain. However, research indicates that it is probably a real phenomenon.

In any case, it is speculated that the myriad cannabinoids (and other compounds) in certain strains work together to determine the final effects. It is not as simple as X amount of THC equals Y high. In the most well-known example of the entourage effect, CBD has been shown to counteract some of the psychotropic effects of THC. So, by moving closer to a 1:1 CBD to THC ratio, the negative effects of THC—such as paranoia and a racing heart—may be reduced.

This is but one example involving only two cannabinoids, but there could be a huge number of different molecules interacting directly and indirectly within the body to influence the overall effect.