1. on the inside; within something
2. within an organization or company; not involving outsiders
3. in one’s mind or thoughts; privately

Examples

• The building was damaged internally by the fire.
• The medicine is taken internally, not applied to the skin.
• The company handled the complaint internally without involving lawyers.
• She was promoted internally after working there for five years.
• He struggled internally with the difficult decision.
• The conflict was resolved internally among team members.
• The pipes were corroded internally and needed replacement.