The process of adding heat to raw cannabinoids in order to activate them.
Decarboxylation is the process of removing a carboxyl group, a group of compounds composed of a carbon double bonded to an oxygen and an OH bonded to that same oxygen. This process is necessary to activate the cannabinoids found in plants. It happens as a result of heat and time.
Summary from Wikipedia:
Decarboxylation is a chemical reaction that removes a carboxyl group and releases carbon dioxide (CO2). Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is the first chemical step in photosynthesis, is called carboxylation, the addition of CO2 to a compound. Enzymes that catalyze decarboxylations are called decarboxylases or, the more formal term, carboxy-lyases (EC number 4.1.1).Read more