Borrowing
Borrowing is simply one language taking words directly from another and using them as its own. One of the biggest ”offenders” of borrowing words from other languages is English, which continues to take in new words. As it turns out, the origin of some very English-sounding words today can be quite surprising: for example, not many people know that the word robot actually comes from Czech, and the literary works of Karel Čapek.
Some languages, like French, remain more resistant to borrowing, instead preferring their own equivalents, but most languages could easily find examples of borrowed words in daily use.