界

(bound form) boundary; border / (bound form) realm

to introduce / to lie between / between / shell / armor

field / farm / CL:片[pian4]

world / CL:個|个[ge4]

cosmos (Buddhism)

upper bound

supremum (math.) / least upper bound

lower bound (math.) / world of mortals / (of gods) to descend to the world of mortals

infimum (math.) / greatest lower bound

Universal Declaration of Human Rights

World Expo / abbr. to 世博[Shi4 bo2]

to fight the whole world (idiom)

(math.) infimum; greatest lower bound

the Three Worlds (as proposed by Mao Zedong), i.e. the superpowers (USA and USSR), other wealthy countries (UK, France, Japan etc), and the developing countries of Asia, Africa and Latin America