1. A computer program product comprising a computer-readable storage device encoded with computer-executable instructions that, when executed by a computing device, perform a method for disambiguating text that is to be converted to speech using lexeme based rules, said instructions comprising: at least one conditional statement for use in a text disambiguation engine of a text-to-speech system, wherein the conditional statement defines a sense of usage for a lexeme and wherein the conditional statement includes a context range specification, the at least one conditional statement including a first conditional statement for determining a sense of usage of a lexeme as an acronym and a second conditional statement for determining a sense of usage of the lexeme as a word, wherein the first conditional statement and/or the second conditional statement distinguishes between the sense of usage of the lexeme as an acronym and the sense of usage of the lexeme as a word at least in part by requiring a specified word within a specified context range of words of the lexeme; a significance indicator associated with each conditional statement, wherein the significance indicator defines a criteria for selecting an associated sense of usage; and in response to selecting a sense of usage corresponding to the lexeme used as an acronym, replacing the lexeme with a defined full text equivalent.