Tetractinal is a term that may not be familiar to many people outside of the scientific community, but it is commonly used in the study of marine sponges. Synonyms for this word include "tetraxon" and "four-rayed spicules." Tetractinal spicules are unique to certain types of sponges and are often used to distinguish between different species. These spicules are made up of four rays or arms that intersect at a central point, giving them a distinct shape and structure. Other terms that may be used in reference to tetractinal spicules include "quadrate," "tetrahedral," and "four-pointed." Overall, tetractinal and its synonyms are important terms in the study of sponge taxonomy and morphology.