How many amino acids exist?

There are 20 amino acids that are active in the human body. In addition to these, there are approximately 250 non-protein-forming amino acids. There are three main types of amino acids that the body processes: essential, nonessential and semi-essential.

Essential amino acids are not to be mistaken as more important than the other types. The term "essential" means that these amino acids have to be taken in voluntarily by the body because it cannot produce these said amino acids on its own. On the other hand, nonessential amino acids refer to those that the body can make on its own. The semi-essential amino acids are those that have to be taken in under certain circumstances.