|Attestation:||enθus, enikes, θiuθis, klu?θurus, kusenkus, lavises, pitis, remies, )s, sφuras, terunies, φelzuries, χaisurus, χaris
Corresponding to the Etruscan genitive I (Rix 1985: 125 f., Wallace 2008: 46). As in Etruscan, the older form of the ending *-si can still be inferred from the pertinentive I ending -si. Very well documented in Raetic, unlike the genitive II (see -l(a)); this imbalance might be attributed to Raetic names tending strongly to end in a vowel, in regard to the phonotactic rule for praenomina (individual names) according to Rix 1985: 127, stating that the genitive II was only used instead of I in names with an auslaut in a dental fricative. Note that genitives in -es and -is are formally identical with ablatives]] in -es and -is (the latter being products of umlaut). On the possibility of genitives originally being adjectives of possession, enabling them to serve as bases for cases (pertinentive, ablative), see Rix 1985: 127.