Decidualization is the process in which cells from the endometrium transform into decidua, a specialized tissue that supports the growth and development of the fetus during pregnancy. Synonyms for this term include deciduarization, decidual reaction, decidualisation, and endometrial decidualization. These terms all describe the same process, which involves changes in the shape, structure, and function of the endometrial cells to prepare for implantation and support of the developing embryo. Understanding the various synonyms for decidualization can be helpful in medical research and discussions related to reproductive health and fertility.