Learn Toki Pona, all 120ish words of it

Toki Pona has about 120 words. That's the whole language, on purpose: Sonja Lang built it in 2001 to see how much you can say with how little. Because there's so little to memorize, the interesting part starts immediately, combining small words into bigger meanings, which is the skill every other language is secretly about.

People reach conversational Toki Pona in weeks, not years. Parlita gets you talking from the first session, and there's no better way to feel the whole arc of learning a language, compressed into a month. toki! is hello. You're already 1% done.

You can learn every word in a weekend. That is not a figure of speech, there are about a hundred and twenty of them and most people have the whole list inside two weeks. Then the real work starts, which is saying what you mean using only the words that exist. There is no word for computer. There is no word for hospital. You build them out of what you have, and two speakers will build them differently.

The grammar is tiny and strict: a handful of particles, fixed word order, no tenses, no plurals, no cases. Because so much of the meaning sits in context rather than in the words, conversations run slower and more deliberately than in any other language here, and speakers tend to describe that as the point rather than a limit. It is also the only one on this list you can be genuinely conversational in within a month.