天际 literally combines 天 (tiān, 'sky' or 'heaven') and 际 (jì, 'boundary' or 'edge'), meaning the visible line where the earth (or sea) appears to meet the sky — the horizon. It is a poetic, slightly literary term often used in descriptive writing, landscape painting, travel narratives, and photography to evoke vastness, openness, or distance.

Unlike the more neutral and everyday word 地平线 (dìpíngxiàn), 天际 carries a subtle aesthetic or emotional weight — it’s frequently found in poetry, song lyrics, or evocative prose describing sunrises, sunsets, deserts, oceans, or mountain vistas. It rarely appears in casual spoken Chinese or technical contexts like navigation or meteorology, where precise terminology is preferred.