When asked to give a talk at a mathematics teacher conference that focused on research in mathematics education, Ruhama Even viewed the invitation as an opportunity to address the meta-question: what can teachers learn from research in mathematics education? The reason for her view was her way of feeling, as a researcher and teacher educator, that the relevance of research in mathematics education deserves explicit discussion. Although research in mathematics education has flourished in the last decades and improving mathematics teaching and learning has always been the overarching goal of researchers in the field, mathematics education research is often accused of having only a minor impact on practice. For research to have an impact on practice, there is a need for it to be relevant for practitioners, and for practitioners to have access to it and be able to use it effectively. Consequently, many teachers are not familiar with research in mathematics education, nor wish to become so. Even's aim was to focus on ideas that both influenced her own thinking about mathematics learning and teaching during her own professional life, and to have the potential to contribute to the development of "knowledge," "courage," and "modesty" in teaching. Even focused on the following ideas derived from a synthesis of research in mathematics education: (1) Mathematical knowledge is constructed in ways that do not necessarily mirror instruction; (2) Mathematical meaning is both subjective and sociocultural; (3) Knowledge and practices of learning and knowing are inseparable; and (4) Knowing is a "slippery" notion. Each of the sections in this article focuses on one of these ideas, highlighting the importance for teachers to be knowledgeable about them.