I was reading through posts on the Nordic Go Dojo blog and I found something interesting in Antti’s article Is the ranking system facing a crisis?
While the Japanese professional go world uses a fair ranking system that depends on the number of wins that one gets in professional tournament games, the amateur system is quite different. One can earn amateur ranking diplomae by participating in regular ranking tournaments and getting a good enough score on a particular level – or else you can just buy a diploma with money.
What is this word diplomae?
The basic English plural would, ofc, be simply diplomas. Antii interpreted diploma as a feminine Latinate noun of the first declension: -a, -ae.
However, diploma is actually a third-declension neuter noun in Latin, with the plural diplomata.
This is the octopus, octopi mistake (octopus in Latin pluralises to octopodes) of believing that there are only three Latin declensions (m. -us, -i; f. -a, -ae; n. -um, -a).