When it comes to the cannabis industry, cultivar and strain are synonymous.
That said, strain scientifically pertains to viruses, as in “viral strain.” Cultivars are different genetics of cannabis.
For example, GG4 and Blue Dream are different cultivars of the same plant: cannabis. These are also known as different genotypes of cannabis; their genetic code is each unique.
Within each genotype (genetic grouping), you can find varying phenotypes, which is the physical expression of the genotype. This explains why there are several versions of cultivars on the market, why there are purple and green versions of most cultivars, etc. Seeds from the same mother plant are each the same cultivar/strain (genotype) but can have varying phenotypes and chemotypes.
So what's a chemovar?
Chemovars have different chemical blueprints (profiles), but can have the same genetics. The chemical expression is impacted by methods of growth, environment, altitude, etc. The same genotype of GG4 grown in two separate gardens will likely have different profiles, and be two different chemovars of the same genotype.