Whether a chamber is or is not a ventricle is determined by its myocardial morphological characteristics, not by the entering atrioventricular (AV) valves. The anatomic characteristics of the morphologically right ventricle and the morphologically left ventricle have been well described, are widely understood, and do not need to be changed. What a ventricle is should not be redefined in terms of the AV connections because such redefinition is based on the classic definition of single ventricle, which itself is not satisfactory. This old definition is wrong in principle, violates the morphological method of diagnosis and designation of the cardiac principle, violates the morphological method of diagnosis and designation of the cardiac chambers, and has two kinds of exceptions. Consequently the classic definition of single ventricle must not be used as a paradigm (model) for the redefinition of what a ventricle is or is not. The approach and terminology based on the use of the unsatisfactory single-ventricle is or is not. The approach and terminology based on the use of the unsatisfactory single-ventricle paradigm approach and terminology based on the use of the unsatisfactory single-ventricle paradigm should be discontinued, eg, "primitive ventricle," "main chamber," "accessory chamber," "trabecular pouch." Being unnecessary, these nonmorphological components of the terminology of congenital heart disease may be omitted. Morphological anatomy, unadorned, is the key to clarity, simplicity, and accuracy.