_fīnis_[84] ＞ fis _mater_ ＞ maire _fĭdes_ ＞ fẹs
_fīnem_ ＞ fi _matrem_ ＞ maire _fĭdem_ ＞ fẹ
_fīnes_ ＞ fis _matres_ ＞ maires _fĭdes_ ＞ fẹs
_fīnes_ ＞ fis _matres_ ＞ maires _fĭdes_ ＞ fẹs
1. Masculine nouns of this type which etymologically had no -s
in the nom. sg., often took one, even in the earliest times.
2. _Laus_ and _res_ were often invariable, but were sometimes
declined like _sols_ and _fes_.
(2) Nouns with a difference of stem but not of accent:--