36. z often stands for ðs as well as ts, as in þēr þykkizk (ye seem) = *þykkið-sk, Vest-firzkr (belonging to the West Firths) = -*firðskr (fǫrðr, firth).
37. Inflectional t is generally doubled after a long accented vowel: fār (few) neut. fātt (cp. allr 'all,' neut. allt), sā (I saw), sātt 'thou sawest.'
Inflections
Nouns
38. Gender. There are three genders in Icelandic--masculine, feminine, and neuter. The gender is partly natural, partly grammatical, generally agreeing with the gender in Old English. Compound words follow the gender of their last element.
39. Strong and Weak. All weak nouns end in a vowel in the nom. sg. and in most of the other cases as well. Most strong nouns end in a cons. in the nom. sg.
40. Cases. There are four cases--nominative, accusative, dative, genitive. All nouns (except a few contractions) have the gen. pl. in -a (fiska, of fishes), and the dat. pl. in -um (fiskum). All strong masculines (fiskr) and some strong feminines (brūðr, bride) take r5 in the nom. sg. Most strong feminines show the bare root in the nom. sg. with u-mutation, if possible (āst, favour, fǫr, journey). The nom. pl. of all strong masc. and fem. nouns ends in r (fiskar, āstir). The acc. pl. of fem. nouns is the same as the nom. pl. (āstir). The acc. pl. of masc. strong nouns always ends in a vowel (fiska). The plur. nom. and acc. of neuters is the same as the sing. nom. and acc., except that in the plur. nom. and acc. they take u-mutation, if possible (hūs, houses, lǫnd, lands).
[Footnote 5: Subject, of course, to the assimilations described above.]
41. The declensions are most conveniently distinguished by the acc. plur.
Strong Masculines