Proto-Greek preserved the gender (masculine, feminine, neuter) and number (singular, dual, plural) distinctions of the nominal system of Proto-Indo-European. However, the evidence from Mycenaean Greek is inconclusive with regard to whether all eight cases continued to see complete usage, but this is more secure for the five standard cases of Classical Greek (nominative, genitive, dative, accusative and vocative) and probably also the instrumental in its usual plural suffix -pʰi and the variant /-ṓis/ for o-stem nouns. The ablative and locative are uncertain; at the time of Mycenaean texts they may have been undergoing a merger with the genitive and dative respectively. It is thought that the syncretism between cases proceeded faster for the plural, with dative and locative already merged as "-si" (the Proto-Indo-European locative plural having been "*-su-"). This merger may have been motivated by analogy to the locative singular "-i-". Nevertheless, seven case distinctions are securely attested in Myceneaen in some domain, with the status of the ablative unclear.