But cases of _ai_, _ae_, which arose later than the change to _ei_, _i_, were unaffected by it; thus the nom. plur. of the first declension originally ended in -_as_ (as in Oscan), but was changed at some period before Plautus to -_ae_ by the influence of the pronominal nom. plur. ending -_ae_ in _quae?_ _hae_, &c., which was accented in these monosyllables and had therefore been preserved. The history of the -_ae_ of the dative, genitive and locative is hardly yet clear (see Exon, _Hermathena_ (1905), xiii. 555; K. Brugmann, _Grundriss_, 1st ed. ii. 571, 601).
The diphthongs _au_, _ou_ in unaccented syllables sank to -_u_-, as in _includo_ beside _claudo_; the form _cludo_, taken from the compounds, superseded _claudo_ altogether after Cicero's time. So _cudo_, taken from _incudo_, _excudo_, banished the older *_caudo_, "I cut, strike," with which is probably connected _cauda_, "the striking member, tail," and from which comes _caussa_, "a cutting, decision, legal case," whose -_ss_- shows that it is derived from a root ending in a dental (see §25 (b) below and Conway, _Verner's Law in Italy_, p. 72).
_Consonants._--Passing now to the chief changes of the consonants we may notice the following points:--
23. Consonant _i_ (wrongly written _j_; there is no _g_-sound in the letter), conveniently written _^i_ by phoneticians,
(i.) was lost between vowels, as in _tres_ for *_tre^ies_, &c. (§ 17. 6);
(ii.) in combination: -_m^i_- became -_ni_-, as in _veniö_, from Ind.-Eur. *[g]^u _m^io_, "I come," Sans. _gam_-, Eng. _come_; -_n^i_- probably (under certain conditions at least) became -_nd_-, as in _tendo_ beside Gr. [Greek: teinô], _fendo_ = Gr. [Greek: theinô], and in the gerundive stem -_endus_, -_undus_, probably for -_en^ios_, -_on^ios_; cf. the Sanskrit gerundive in -_an-iya-s_; -_g^i_-, -_d^i_- became -_^i_- as in _maior_ from *_mag-ior_, _peior_ from *_ped-ior_;
(iii.) otherwise -_^i_- after a consonant became generally syllabic (-_i^i_-), as in _capio_ (trisyllabic) beside Goth. _hafya_.
24. Consonant _u_ (formerly represented by English _v_), conveniently written _^u_,
(i.) was lost between similar vowels when the first was accented, as in _audiui_, which became _audii_ (§ 17 [6]), but not in _amaui_, nor in _avarus_.