For more than a century, the Greek suffix -μός/-μος has been the subject of many morphological, semantic and comparative studies. Despite this abundant scientific literature, many questions still remain unanswered. First of all and quite strikingly, general agreement is still wanting, for morphological studies, on the formal criteria that should guide a descriptive analysis of this suffix. Secondly, many semantic studies bring out only a very vague meaning for this suffix. Furthermore, these studies generally take into account a single formal criterion (the suffixal accent) in their analysis of this meaning. Finally, comparative studies almost unanimously try to reconstruct a single original type in *- mo- which appears to be quite inappropriate in order to explain the historical situation of Greek -μός/-μος nouns. All these facts lead us to consider that the time has come to reexamine this subject.