Bouin solution is a histological fixative used to preserve tissue samples. However, there are a few common synonyms for the solution that researchers may come across. One is Carnoy's fixative, which is another popular tissue fixative. Another synonym is Zenker's fixative, which is used for preserving delicate tissues. PFA (paraformaldehyde) is another synonym, which is a commonly used fixative for electron microscopy studies. Finally, formalin fixative can also be used as a substitute for bouin solution, although it may not be as effective at preserving delicate structures. Overall, these synonyms can be useful to know when selecting a fixative for tissue samples.