Milinkovic, NenadMaričić, SanjaLazić, Bojan2023-03-082023-03-0820221451-673Xhttps://scidar.kg.ac.rs/handle/123456789/17069Correct understanding of the equals sign is the key to understanding arithmetic, and a fundamental concept important for learning other areas of mathematics. Research around the world repeatedly mentions problems with correctly understanding the equals sign, emphasising the limited view of the equals sign as a command ”to calculate“ among students. The goal of the research was to identify the development of the concept of equality in line with the operationalised levels (operational, relational, and relational in the context of real-life problem solving) and determine differences in understanding between students of the second (N = 190) and the fourth (N = 210) grade of primary school. The research was carried out using the testing technique. The research results show that students do not possess sufficiently developed relational understanding of the equals sign and that operational understanding prevails. Students of the fourth grade demonstrated better understanding of the equals sign at all levels of understanding than the second graders.enCC0 1.0 Universalhttp://creativecommons.org/publicdomain/zero/1.0/equals signequivalenceoperational understandingrelational understandingmathematicsmathematics educationarticle10.46793/Uzdanica19.S.095M