Things that are interchangeable can be exchanged with each other without it making any difference.
例句
His greatest innovation was the use of interchangeable parts...他最大的革新在于使用了可互換的零件。Every part on the new models is interchangeable with those on the original.新款上的每一個零部件與原先的都可互換。
英漢詞典釋義
adv.
可交換地;可替換地
These two words can be used interchangeably.這兩個字可以換用。