The prefixes ENTO and ENDO both denote the concept of 'INSIDE'. ENTO is a Greek prefix derived from the word 'entos' meaning 'WITHIN', while ENDO is a Latin prefix derived from the word 'endo' meaning 'INWARDLY'. Both prefixes are used to describe something that is located INSIDE or WITHIN something else. For example, an entomologist is someone who studies insects, which are located INSIDE their environment. Similarly, an endocrinologist is someone who studies hormones, which are located INSIDE the body.