A plausible reconstruction for the participle of the intransitive forms is Proto-Basque*eizani,[1] while *edun can be reconstructed for the transitive ones.[2] The verb forms in each paradigm have different etymologies:
NOR: from the participle prefix *e- + the stem -iza- (of unknown origin) + the past participle suffix -n. It has numerous suppletive stem forms. The present-tense forms have three stems: -a (third-person singular only), -aiz (with first- and second-person singular prefixes), and -ara (in first- and second-person plural forms).
NOR-NORI: the stem -(t)zai- occurs in the indicative forms. The potential and imperative forms have the suppletive stem -ki-. Forms with plural nor agreement throughout the paradigm have the suffix -zki- immediately attached the stem and preceding the nori agreement suffixes.
NOR-NORK: the stem -(d)u- forms the basis of the indicative forms. This stem also appears in the dialectal participle eduki. A verbal noun edutzea is attested from the fifteenth century, derived from either eduki or *edun. The potential and imperative forms are built on the stem -za- which becomes -tza- after a prefix ending in n.
NOR-NORI: the stem is -i- in the indicative, and -ieza- in the potential and imperative. As in the nor-noriizan paradigm, forms with plural nor (absolutive) agreement are suffixed with -zki-. This marker is attached directly to the stem and precedes other agreement suffixes.
Southern Basque (like Spanish) has two different verbs that are usually translated to English as “to be”: izan and egon. The former is used to express a quality of something (the first two examples), while the latter (the third and fourth examples) is used to express a location or a temporary state. Northern Basque does not have this distinction, so "to be" can be translated as izan in almost all contexts.
Mahaia handia da. ― The table is big.
Iñaki Donostiakoa da. ― Iñaki is from San Sebastián.
Mahaia zikina dago. ― The table is dirty.
Iñaki Donostian dago. ― Iñaki is in San Sebastián.
Light verb constructions with egin(“to do”) usually take nor nork auxiliaries, even when translated by intransitive verbs.
In Northern dialects the citation form ukan is used for the transitive senses, with izan reserved for the intransitive ones.
The tenses are referred to by the names given in the 1979 standarization of verbal forms, with the exception of the consequential indicative forms. This is the most common notation in non-specialist textbooks and learning materials.
In linguistic contexts, the nor and nor nori forms of the potential, subjunctive and imperative moods are usually classified as belonging to a reconstructed verb *edin. The 1997 standardization of verbal forms uses this analysis.
Basque grammarians usually refer to the nor nork and nor nori nork auxiliaries by the northern citation form ukan or by the reconstructed participle form *edun; as a different verb from the intransitive forms of izan. The forms belonging to the potential, subjunctive and imperative moods belong to a different reconstructed verb, *ezan.
1. Hypothetical citation form lacking non-finite forms, the non-finite forms of izan, ukan and eduki are used instead. 2. Verb lacking finite forms, *edun is used instead. 3. *edun is also used synonymously.
