Pair-rule genes are a set of genes that are crucial in the development of segmented organisms, such as insects. These genes are responsible for dividing the embryo into distinct segments during early embryonic development. Synonyms for pair-rule genes are segment polarity genes, which control the development of individual segments within the embryo, as well as segmentation genes, which determine the overall number and placement of segments. Other terms used to describe pair-rule genes include segment specification genes, patterning genes, and boundary genes. Understanding the function of pair-rule genes is of great importance in developmental biology, as their dysfunction can lead to severe developmental abnormalities.