Internal means existing or happening on the inside of something, as opposed to the outside or surface. Your internal organs are the ones inside your body, like your heart, lungs, and stomach, while your skin is external. A building's internal walls divide up the space inside, while its external walls face the street.

The word also describes thoughts and feelings that happen privately within a person. When you have an internal conflict, you're wrestling with competing thoughts or feelings inside yourself: maybe part of you wants to try out for the play while another part feels nervous about performing. An internal dialogue is that voice in your head when you're thinking through a problem or decision.

In organizations, internal describes things that stay within the group. A company might send an internal memo only to its own employees, not to customers or the public. A school's internal policies govern how teachers and students behave within the school.

The opposite of internal is external, which means outside or coming from beyond something. When a doctor examines you, they check for both internal problems (inside your body) and external signs (what they can see on the surface). Understanding what's happening internally, whether in your body, your thoughts, or an organization, requires looking deeper than what's visible on the outside.