[ELI5] How the explorers establish sufficient shared vocabulary with people from different country?

Question

I just finished watching Arrival movie (the one with Amy Adams and Jeremy Renner). And it got me wondering how do people actually communicate when they first immigrate / trade with other people from different language and culture, I mean like how they get people to create like the “dictionary”? how can they explain what the words mean in their language.

TIA

In: 2

Answer 1

Everyone knows what a tree looks like. You point at a tree and say “tree”. They respond with “havgshehhsyhsbsh”. You now know that tree in their language is havgshehhsyhsbsh.
Repeat this with other things, combine with hand gestures/body movements and you have a fairly good start.