The purpose of the study: This paper aimed at describing the teachers' competence in the acquisition and use of the language of mathematics at public and private senior high schools all over Malang City, Malang Regency, and Batu City, Indonesia.
Methodology: Qualitative descriptive research design was employed by means of content analysis on the results of the interview and documents of mathematic instructions designed by 30 teachers who also served as the research subjects, spiral analysis on the qualitative data by Creswell was applied to analyze the data, with the support of NVivo 12 plus software.
Main Findings: This research has revealed that the teachers have acquired and used the language of mathematics, with some errors and fallacies in the use of mathematics vocabularies, grammar, and the explanation of mathematical symbols. The teachers' competence in the acquisition and use of the language of mathematics was influenced by the knowledge about mathematical concepts, presentations, and instructions.
Applications of this study: The findings of this study are expected to add new knowledge about the competency of the mathematics language of the teacher so that it can be used as a reference for colleges producing teacher candidates in developing the curriculum. Theoretically, these results can be used as a reference and contribute to assessing the mathematical language competence of teachers.
Novelty/Originality of this study: This current research, is based on their educational qualifications, and to identify factors that influence the teachers' competence in the acquisition and use of the language of mathematics which is less explored by the earlier researcher.