The word men is not an example of the weak inflection, since it was produced by i-mutation of man.
Augen) have a mixed inflection, being strong in the singular but having the characteristic -en plural ending of a weak noun.
In the Icelandic language, nouns are considered weak if they fulfill the following conditions: Masculines: An example of the latter is nemandi (student), plural nemendur.
The words bóndi (farmer) and fjandi (enemy or the devil or a demon) belong to this class with some irregularities.
Both, incidentally, end in -ja in the oblique cases (Grikkja is the accusative, dative and genitive for one Greek).