[Jprogramming] The role of the . in J words

[Sherlock, Ric]

I am working with the maintainer of GeSHi (syntax highlighter used on Rosetta Code) to improve support for J.

As part of that process I'm seeking clarification of the role of the fullstop character (.) as it appears in J words, eg:  (do.) (for.) (p.) (p..) (*.) (.) (.:) (..)

Is the fullstop 
 A) a symbol to control language flow,
 B) an integral part of the word,
 C) some other better description?

Or slightly differently:
Is the fullstop
  A) syntax/punctuation,
  B) spelling,
  C) sometimes one, sometimes the other?