海岸 (hǎi àn) literally combines 海 (hǎi), meaning 'sea', and 岸 (àn), meaning 'shore' or 'bank'. Together, they refer specifically to the land area where the sea meets the land — the seashore or coastline. It emphasizes the boundary zone itself, not just the water or the beach sand, and often implies a natural, geographical feature rather than a developed area like a seaside resort.

This word is commonly used in geography, travel writing, environmental discussions, and everyday descriptions of coastal scenery. It appears in compound terms like 海岸线 (hǎi àn xiàn, 'coastline') and 海岸保护 (hǎi àn bǎo hù, 'coastal protection'). While it can be used broadly, it carries a slightly formal or descriptive tone — you’d more likely read it in a guidebook or news report than hear it in casual speech among friends at the beach.