In the learning of mathematics, students' oral and written vocabulary can inform about some concepts and their form of mental representation. This is one of the objectives proposed in this study. For this, a test was implemented that addresses six mathematical concepts linked to the numerical system and positional value. The sample included 40 students from Santiago Chile from three educational centers (municipal, private subsidized and private) randomly selected, with an age range of 10 to 17 years. The analysis of the results evidenced the importance of vocabulary in specific contexts to access lexical availability and its associated concepts. This line of research allows to study lexical categorizations and expand the field of vocabulary instruction in mathematics. One conclusion of the study is the teaching of mathematics as a language and not as a mere procedure.