A library is a collection of functions that can be used by a program or another library.
- the official standard library of built-in Tcl procedures
- A Tcl repository
- a guide to libraries, packages, modules, extensions, etc., for Tcl
"Library" means different things here, all different from the popular concept "a building with many books inside":
- Tcl and Tk both are delivered as shared libraries.
- In a typical distribution, there is a lib dir, which contains directories like tcl8.3 and tk8.3, which contain Tcl scripts and other packages.
- A popular Tcl-only extension is Tcllib, the "Tcl library", and its young brother Tklib
Just to make things a little less unclear... RS