na-adjective
Describes a smooth, shiny, and attractive surface, often used for hair, skin, or fabric. Carries a refined, elegant nuance.
彼女の髪はいつも艶やかで美しい。
Her hair is always glossy and beautiful.
この絹のドレスはとても艶やかだ。
This silk dress is very lustrous.
Derived from the noun 艶 (つや, 'gloss') with the adjectival suffix やか, which forms na-adjectives expressing a state or quality.