1) Ordinary language. Here the term ordinary denotes the language current in the everyday vocabulary of any particular child, which will, of course, vary for pupils of different ages and stages of understanding.
2) Mathematical verbal language. Verbal here means “using words,” either spoken or written.
3) Symbolic language. This type of communication is made in written, mathematical symbols.
4) Visual representation. Although not strictly a “language.” this is certainly a powerful means of mathematical communication.
5) Unspoken but shared assumptions. Again, these do not really fall within the definition of “language,” but they are a means by which mathematical understanding is communicated and on which new understanding is created. They are ignored at one’s peril.
6) Quasi-mathematical language. This language-usually, but not exclusively, that of the pupils-has, for them, a mathematical significance not always evident to an outsider (who may well, in this context, be the teacher).