Heavy rain is expected in the Tōkai region tomorrow.
Tōkai is a region where the automobile industry is thriving.
eastern sea; sea to the east
Literal Sino-Japanese use meaning a sea lying to the east. In ordinary modern prose, 東の海 is often more transparent, while 東海 tends to sound compact, formal, or name-like.
In the old geography book, the sea spreading east of that country is called the eastern sea.
Tōkaidō; Edo-period Edo-Kyoto highway
Historical abbreviated use for 東海道, especially the Edo-period highway linking Edo and Kyoto. This is not the usual modern way to refer to the road or route.
See also: 東海道
In Edo-period materials, Tōkaidō is sometimes abbreviated and written as 東海.
Archaic and poetic use for Japan, especially in literary or classical-style contexts. Modern Japanese normally uses 日本 or similar names instead.
In classical texts and Chinese-style poetry, 東海 can refer to Japan.
南海 and 東海 share the same 〜海 pattern but point in different directions—south versus east—so learners can mix up which region they refer to.