The Proto-Turkic word *gün(eĺ) / guńaĺ
Word *gün(eĺ) / guńaĺ
Meaning sun, day, sunny place, sun-heat

Comments
S. A. Starostin, A. V. Dybo, O. A. Mudrak - An Etymological Dictionary of Altaic Languages, 2003, Brill

Other words that might be of interest
*jar- ‘to shine, to dawn, light’, *bulut ‘cloud’, *köl- ‘shadow, to shadow’, *jal-ɨn ‘flame’, *ört ‘flame, to burn, steppe fire, to get burnt’, *ōt ‘fire’, *āń(k) ‘moon, month’, *ōču- ‘thin, light, easy, worthless, youngest, to diminish’, *bus ‘steam, fog’, *tüt- ‘smoke’, *jul-du-ŕ ‘star’, teŋri ‘god, sky, heaven’