A command is what other languages call a function, routine or reserved wordreserved wordA reserved word is one that "looks like" a normal word, but is not allowed to be used as a normal word. Formally this means that it satisfies the usual lexical syntax (syntax of words) of identifiers – for example, being a sequence of letters – but cannot be used where identifiers are used.
› wiki › Reserved_wordReserved word - Wikipedia, and can be defined by the "proc" command or in C or whatever. A statement is an invocation of a command. Using traditional definitions, a statement in Tcl is a command followed by zero or more arguments.Sep 25, 2009