phenomena 和phenomenon那一个是复数形式?

phenomena 和phenomenon那一个是复数形式?
以下是Meriiam—Webster的解释：
Main Entry:phenomena
Pronunciation:fi-*n*-m*-n*,-*n*
Function:noun
Inflected Form:plural -nas
Date:1576
nonstandard :PHENOMENON
usage Phenomena has been in occasional use as a singular for more than 400 years and its plural phenomenas for more than 350.Our evidence shows that it is primarily a speech form used by poets,critics,and professors,among others,but one that sometimes turns up in edited prose *the Borgia were,in modern terms,a media phenomena Economist*.It is etymologically no more irregular than stamina,agenda,and candelabra,but it has nowhere near the frequency of use that they have,and while they are standard,phenomena is still rather borderline.
只是说phenomena的nonstandard form 是phemonenon...疑惑