Internal means inside — the opposite of external. An interval is a gap between two points, in time, space or music. An internal investigation; a ten-minute interval. One is an adjective about location; the other is a noun about spacing.
The core difference
- internal — on or of the inside; within an organisation or body. Internal organs, an internal memo, internal affairs.
- interval — a gap between two things; a pause in a performance; in music, the distance between two notes. At regular intervals, the interval is twenty minutes, an interval of a fifth.
The tell
Internal ends in -al like its opposite external, and it describes. Interval ends in -val, from the Latin for a rampart — it is the space between two walls, and it names a gap. If you can put an or the in front and a length after it, it is an interval.
In use
- internal — The company opened an internal investigation. The patient had internal bleeding.
- interval — There will be a short interval after the first act. Check the readings at hourly intervals.
Common slips
- an interval investigation → an internal investigation
- a ten-minute internal → a ten-minute interval
Internal is inside; interval is in between.
Where the words come from
Internal is from Latin internus, "inward", from inter "within". Interval is from Latin intervallum, "the space between ramparts" — inter "between" + vallum "wall", the same vallum that gives us wall. The musical and theatrical senses are both that gap.
