Vectors, one-dimensional arrays of values.
[how does a vector differs from an array?]
2006-10-30,Jaf: I'd rather think of a list as a vector than of an array as a vector.
A vector has an implicit association of its contents to the base vectors, e.g., first number of the vector is the first coordinate that says "how many" of the first vector from the base are within the vector we are looking at.
Reading this again I think I made it more obscure than it was. But I can't find another wording, if one of you would step in for help....
As for the reprensentation of vectors inside a program, well, either lists or arrays can be used; I think it depends on what one wants to do with the vector elements.
In pure-Tcl, lists are most appropriate for representing vectors.