- Something's base is its lower part; the solid part that touches the floor or touches the earth and keeps the other parts of the thing up.
- Synonym: foundation
- Something's base is its most important part.
- A base is a building for military personnel and material.
- (chemistry); (countable) An base is a chemical that releases hydroxide ions in water, and has a high pH.
- Synonym: alkaline
- Antonym: acid
- Ammonia is a weak base.
- Rude, unfair, or unkind.
- Synonym: immoral
- The people who make those sex videos are really base.
- (transitive) When something or someone is based in a place, they do most of their work in that place.
- The airline is based in Toronto, but flies all over the world.
- (transitive) If you base x on y, you build or make x on, using, or to be like y.
- The movie is based on the book.