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seis (Cardinal Number) "six"
12th cent. Old Spanish seis, uncommon seyes (probably under analogy from leyes). From Latin sex 'id.' From Proto-Italic *seks 'id.' From Proto-Indo-European *u̯ek-s 'id.'
Indo-European
Romance
Asturian seis, Portuguese seis, Galician seis, Catalan sis, French six, Italian sei, Aromanian shasi, Romanian șase, Sardinian ses
Celtic
Celtiberian sues "six," meaning uncertain, Old Irish 'id.,' Middle Welsh chwech 'id.,' Old Breton hue 'id.,' Cornish whegh 'id.'
Germanic
Gothic saihs "six," Old Norse sex 'id.,' Old High German sehs 'id.,' Old Saxon sehs 'id.,' English six
Albanian
Albanian gjashtë "six"
Balto-Slavic
Old Church Slavonic šestь "six," Russian šest' 'id.,' Czech šest 'id.,' Polish sześć 'id.,' Slovene šę̑st 'id.,' Lithuanian šešì 'id.,' Latvian seši 'id.'
Hellenic
Ancient Greek ἕξ (héks) "six," Doric ϝέξ (wéks) 'id.'
Armenian
Armenian vec' "six"
Indo-Iranian
Sanskrit ṣáṣ- "six," Young Avestan xšuuaš 'id.'