noun
binder
BYN-der/ˈbaɪndər/
A person or thing that holds material firmly together.
The open binder secures the punched sheets with three metal rings.

Etymology
Bind plus the agent ending originally named a person who binds. The word later also named objects that do the holding, including a cover that keeps loose papers together.
In context
She withdrew a binder thick, at least 3 in with a clear plastic cover through which a title page was visible.
More examples
- Egg acts as a binder in the mixture.
- The machine works as a binder for harvested stalks.
- He wears a comfortable chest binder beneath his shirt.
Forms
binder · binders
Similar words
- folder
- Holds papers without necessarily fastening them together.
- adhesive
- A substance that joins surfaces by sticking.