the vocalism of a verb's subjunctive. This includes the root ablaut of subjunctive classes i and v, which tend to co-occur with imperative class i. Optative and imperfect The optative and imperfect have related formations. The optative is generally built by adding i onto the subjunctive stem. Tocharian B likewise forms the imperfect by adding i onto the present indicative stem, while Tocharian A has 4 separate imperfect formations: usually ā is added to the subjunctive stem, but occasionally to the indicative stem, and sometimes either ā or s is added directly onto the root. The endings differ between the two languages: Tocharian A uses present endings for the optative and preterite endings for the imperfect, while Tocharian B uses the same endings for both, which are a combination of preterite and unique endings (the latter used in the singular active). Endings As suggested by the above discussion, there are a large number of sets of endings. The present-tense endings come in both thematic and athematic variants, although they are related, with the thematic endings generally reflecting a theme vowel (PIE e or o) plus the athematic endings. There are different sets for the preterite classes I through V; preterite class VI; the imperative; and in Tocharian B, in the singular active of the optative and imperfect. Furthermore, each set of endings comes with both active and mediopassive forms. The mediopassive forms are quite conservative, directly reflecting the PIE variation between -r in the present and -i in the past. (Most other languages with the mediopassive have generalized one of the two.) The present-tense endings are almost completely divergent between Tocharian A and B. The following shows the thematic endings, with their origin: Comparison to other Indo-European languages In traditional Indo-European studies, no hypothesis of a closer genealogical relationship of the Tocharian languages has been widely accepted by linguists. However, lexicostatistical and glottochronological approaches suggest the Anatolian languages, including Hittite, might be the closest relatives of Tocharian. As an example, the same Proto-Indo-European root (but not a common suffixed formation) can be reconstructed to underlie the words for 'wheel': Tocharian A wärkänt, Tokharian B yerkwanto, and Hittite ḫūrkis. Contact with other languages The Tocharian language stood in contact with various surrounding languages, including Iranian, Uralic, Turkic, and Sinitic languages. Tocharian borrowings, and other Indo-European loanwords transmitted through the Tocharians towards Uralic, Turkic and Sinitic speakers, have been confirmed. Influence onto