the taking of people prisoner in war, and what it produces: both the condition of captivity and the people held captive
This word grows out of the verb "to take captive," and it covers the whole reality of being carried off by an enemy. Depending on the sentence, it points either at the state a person or nation falls into (captivity, and so exile) or at the people themselves who have been seized (the prisoners, the body of captives taken in battle).
The two are really one idea seen from two sides. War produces prisoners, and those prisoners then live in the condition of captivity, so the same word slides easily between them. When the Bible says a people "go into captivity," it names the condition; when it counts "the captives" alongside the rest of the plunder, it names the people. Context, not the word itself, tells you which is in view.
In the prophets the word carries enormous weight, because Israel's own captivity in Babylon became the defining catastrophe of its history. To "go into captivity" was the threatened end of the nation, and "the captivity" became a way of naming the exiled community itself, the people who would later return.