These are all words for the land beside or near to the sea, a river or a lake.以上各词均指海滨、河岸或湖畔。
coastthe land beside or near to the sea or ocean指海岸、海滨：◆a town on the south coast of England英格兰南海岸的一座城镇◆The coast road is closed due to bad weather.由于天气恶劣，滨海公路暂时封闭。NOTEIt is nearly always the coast, except when it is uncountable.除用作不可数名词外，coast 几乎总是与 the 连用：◆That's a pretty stretch of coast.那是一段美丽的海岸线。
beachan area of sand, or small stones, beside the sea or a lake指有沙石的海滩、海滨或湖滨：◆She took the kids to the beach for the day.她带了孩子去海滩玩一天。◆sandy beaches沙滩
seaside(especiallyBrE) an area that is by the sea, especially one where people go for a day or a holiday尤指人们游玩、度假的海边、海滨：◆a trip to the seaside去海滨旅行NOTEIt is always the seaside, except when it is used before a noun.除用于名词前外，seaside 总是与 the 连用：◆a seaside resort海滨胜地The seaside is British English; in American English seaside is only used before a noun. * the seaside 为英式英语，在美式英语中，seaside 只用于名词前。
coastlinethe land along a coast, especially when you are thinking of its shape or appearance指沿海地带，尤其是海岸线、海岸地形或轮廓：◆California's rugged coastline加利福尼亚州崎岖的海岸线
sanda large area of sand on a beach指沙滩：◆We went for a walk along the sand.我们去沙滩上散了散步。◆a resort with miles of golden sands有着绵延数英里金色沙滩的度假胜地
the seashorethe land along the edge of the sea or ocean, usually where there is sand and rocks通常指有沙石的海岸、海滨：◆He liked to look for shells on the seashore.他喜欢在海滨捡贝壳。
beach or seashore?用 beach 还是 seashore？
Beach is usually used to talk about a sandy area next to the sea where people lie in the sun or play, for example when they are on holiday/vacation. Seashore is used more to talk about the area by the sea in terms of things such as waves, sea shells, rocks, etc., especially where people walk for pleasure. * beach 通常指海边的沙滩，人们度假时可以躺着沐浴阳光或玩乐；seashore 多指有海浪、贝壳、岩石等的海岸，尤指人们散步消遣的海滨。