What does the prefix "ecto-" refer to in terms of location?

The prefix "ecto-" is derived from Greek and means "outside" or "external." In various scientific and medical terms, it indicates that something is located on the outer side or surface of a structure. For example, in anatomy, "ectoderm" refers to the outermost layer of cells in an embryo. This prefix helps to convey spatial relationships, identifying elements that are positioned externally relative to other structures. Understanding this prefix is crucial for interpreting terminology accurately in contexts such as biology, medicine, and various scientific fields.