ATP stands for adenosine triphosphate, meaning adenosine bound to:

1. The prefix tri- counts the phosphate groups. 2. Adenosine triphosphate is comprised of adenosine bound to three phosphate groups. 3. Adenosine itself is the base adenine joined to the five-carbon sugar ribose. 4. Removing one phosphate gives adenosine diphosphate, which carries two. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 6 'Metabolism', sections 6.1-6.5_