I picked 'associations'. We've been taught to associate words with meaning. It's annoying when you can't find quite the right words or, when the definitions don't quite fit what you mean but, I think they do an impressive job overall. We can communicate with one another and understand really complex ideas. Even fictional stories. That's pretty cool.
I find other languages fascinating. Not that I have any desire to learn them but that varying languages construct a sentence in vastly different ways.
Do you ever wonder about animals? How much they communicate with one another? What they say? How many 'words' they know?