Mathematics has the potential for being spoken ambiguously. This is problematic for many students, in particular those who have disabilities that inhibit processing of printed material. This paper documents the magnitude of potential ambiguity arising from textbooks and provides a measure of the degree to which potential ambiguity is actualized through teachers' speech. Inconsistency among teachers in speaking mathematics is also documented. Evidence is provided that teachers are not adequately aware of ambiguity in speaking mathematics and that they believe that they should have training regarding ambiguity in communication of mathematics and how to speak mathematics non-ambiguously.