Suffix used to denote a social or professional sphere, such as 芸能界 (show business) or 政界 (political world).
彼は芸能界で有名だ。
He is famous in the entertainment world.
He entered the entertainment world when he was young.
政界に入るにはコネが必要だと言われる。
It is said that connections are necessary to enter the political world.
Taxonomic rank in biology; used in terms like 動物界 (animal kingdom) and 植物界 (plant kingdom).
生物は五界に分類されることがある。
Living things are sometimes classified into five kingdoms.
erathem (geology)
Geochronologic unit; used in terms like 古生界 (Paleozoic erathem).
古生界は約5億4千万年前から2億5千万年前までの地層を含む。
The Paleozoic erathem includes strata from about 540 million to 250 million years ago.
Used in physics for a region of influence, e.g., 電界 (electric field) or 磁界 (magnetic field).
電界の強さを測定する。
Measure the strength of the electric field.
Rare standalone noun meaning a dividing line or limit; more commonly encountered in compounds like 境界 (boundary) or 分界 (division).
「界」という漢字は、もともと境目を意味した。
The kanji 界 originally meant a boundary.
She is active and successful in the music world.
境界 is the everyday word for a boundary or dividing line, while standalone 界 with this meaning is rare and mostly seen in old or literary usage.
界 and 階 are both pronounced かい, but 界 means a sphere or world (as in 政界) while 階 is the counter for floors or stories of a building.
界 and 会 share the reading かい, but 界 denotes a social or professional world (like 学界) while 会 means a meeting, gathering, or association.
the world; society; the universe · sphere; circle; world · world-renowned; world-famous · Buddhist realm; space
industry; business world; business circles
limit; bound; boundary
best in the world; number one in the world
boundary; border; limit
neighborhood; vicinity; area · community; scene; fandom
field of vision; visibility; view
political world; political circles; world of politics
The kanji 界 originally depicted a boundary or division between fields. As a suffix, it came to denote a delimited sphere or world. The standalone noun sense 'border' is now rare.
demon world; realm of demons
death; the next world · pass away; die
financial world; business circles
boundary; threshold · criticality; nuclear criticality · critical; at the critical point
outside world; external world; physical world
the heavens; the skies; celestial sphere · heavenly realm; deva realm
interface
hades; realm of the dead; underworld
spirit world; spiritual realm
baseball world; baseball circles
various fields; all walks of life; each sector
the earth below; the ground below · this world; the earthly realm
political and business circles; the political and business establishment
academic world; academia; scholarly circles
magnetic field
legal circles; the legal profession
electric field
sumo world; world of sumo
human realm; spiritual realm of humanity
human world; world of man
three realms of existence · whole universe enlightened by Buddha · past, present, and future existences · far-off ...; distant ...
hades; realm of the dead; the netherworld