上义词是对事物的概括性、抽象性说明；下义词是事物的具体表现形式或更为具体的说明。以immigrate和emigrate以及migrate之间词义关系为例说明如下：
immigrate: 移居入境；To enter and settle in a country or region to which one is not native.
Britain immigrated many colonists to the New World.
英国把大量殖民者移居到了新大陆
emigrate：移居出境，也就是通常说的移民（v）；To leave one country or region to settle in another.
His family emigrated to the U.S. last winter.
他们一家去年冬天移民到美国了。
migrate：移动, 移往, 移植, 随季节而移居, (鸟类的)迁徙
After the Nazis came to power in Germany, many scientists emigrated (that is, left Germany).
纳粹夺取了德国的政权之后，许多科学家都迁走了（也就是说，离开了德国）。
The promise of prosperity in the United States encouraged many people to immigrate (that is, move to the United States).
兴旺发达的前景吸引了众多的移民到美国（也就是指，迁入了美国）
immigrate和emigrate意思相反，一个是移进，一个是移出，而migrate可以说是immigrate和emigrate的上义词。
