Give learning Japanese a try. It's a meta-learning adventure! There are 3 distinct classes of characters (two syllabaries that each have a perfect matching pair with the other, 46 each plus some compounds) and the third are (mostly) chinese Kanji characters. Fun stuff!

I wonder if there is a similar "Pareto priciple"-esque approach that one could use to learn Japanese.

There are the "radicals" which can help you to interpret a new kanji, since they're the kanji building blocks.

I highly recommend this site for that. https://kanji.koohii.com/ which goes along with the book "Remembering the Kanji" by James Heisig (strictly speaking, you don't need the book, but I think it will help understand the idea behind the process). But the stories (mnemonics) on the website are better than the ones in the book, but also let you put in your own stories. You can also vote and choose existing stories, so there are crowd sourced mnemonics that other people have said work for them. One interesting side effect of that is a lot of people decided to use Spider Man whenever there is a "thread" radical, for more memorable stories. I did it around 15 years ago and learned how to write all the 2000+ commonly used kanji in a few months (9 months for me; 2-3 months for a more diligent person). It uses a spaced repetition system (Lietner box method).

Kinda!

The frequency of words in every human language follows the Zipf distribution, which is a power law, like the pareto distribution.

Some learners create what are called frequency lists, which are lists of the most common words, and learn those words first. In general, you get (disproportionately) more bang for your buck from learning the most common words than the rarer words when it comes to understanding.

However, due to the very long tail of word frequency distributions, you eventually need to just start learning words as they come and stop trying to over-optimize with a frequency list.

No. Apart from grammar etc. you‘re missing, you might understand nothing while knowing 80% of the words.

Depending on your definition of "understanding".

If it means you can at least take an educated guess on what a sentence means, then yes.

If it means to understand a sentence like a native speaker does (just slower), then no.

> Can I really understand 75% of text if I have perfect recall of those 800 words?

This thing you're talking about is called 'word coverage'. It's the percentage of words you know in a given text. I've created lots of word coverage graphs in the past, and, as research has shown, you won't really be understanding much until you reach the high 90s in terms of word coverage. The famous number for being able to read English texts extensively requires a word coverage of around 98%. And while it depends on the text, in order to reach 98%, you generally need to know around the top 5k words in a language.

Funny enough, when you understand 75% of the words in a text, you subjectively feel like you're understanding like 10% of what's going on.

This is exactly correct.

With graded readers, thou, you can have good reading experiences with around 3k words (ofc depending on language, book, etc).

The Oxford Bookworms collection has a 400 headword level that includes quite a few interesting ~45-50 page stories. Their 700 headword level is more interesting of course, but for popular like English or Spanish there are a lot of options even for very early stage learners.

Yep, 75% coverage is too low for significant comprehension. You normally need 95% for decent comprehension and 98% for comfortable reading.

The coverage required in Japanese (my target language) seems something like the most frequent 15,000 words (depending on the definition of word) are required for 98% coverage. At 12,000 words it becomes viable to read with some comprehension and semi-frequent dictionary lookups.

Also, interestingly, you need about 2x the number of words in Japanese as English to reach 87% coverage:

"It has been reported that 2,000 high-frequent English words cover 87% of tokens (Nation, 1990). In case of Japanese, 4,024 SUWs are required to cover 87% of tokens." (Text Readability and Word Distribution in Japanese, Satoshi Sato)

You sound like my kind of nerd!

You might wanna check out this analysis I did last week: https://cij-analysis.streamlit.app/

I do a little bit of Japanese word coverage analysis in it, among other things.

In my experience, the words that carry the most information in a sentence are the less common ones. Here's what understanding 80% of a sentence is like:

"I went to the sdjfkdsh and got a new ghjsakgfh."

The missing words could be "dealership" and "truck" or "embassy" and "passport" or quite a lot of other pairs that change the topic entirely, so reading or listening to something with 80% understanding generally requires a dictionary in one hand to get you up to a reasonable level of comprehension. That said, I personally think language learning is enjoyable and rewarding, and tackling the most common word list is a good first step.

This post will give you a sense of what understanding 80% of the text looks likes https://www.sinosplice.com/life/archives/2016/08/25/what-80-...

800 is definitely too little. I'm building a language learning app based around this exact strategy. Right now, I've around 7000 German lemmas tracked in the app and still regularly encounter sentences which I don't understand, because I lack the vocabulary.

While the answer to your question is "no", there is still something you'll be able to do: to express yourself and to understand spoken language.

Like other people said here, understanding will probably still be limited, esp. in writing. But expressing even complex things becomes easier.

E.g. instead of saying "Do you have medication against migraine" at a pharmacy you could say "Do you have something for pain here" while pointing at your head.

This is what we call fluency, and starting at 800 words I would argue you have basic fluency in the language. And also regarding understanding spoken language – those words might be enough to express that you haven't understood something and ask people to simplify.

Words are not enough, though – pronunciation and grammar also play their part.

No. Just memorizing words won’t get you there. Looking up the definition of “go” and memorizing it won’t teach you that “go over” means review, that “go under” means to go out of business, that “go on” means to continue, etc, etc, etc.

You need a lot of input before you’ll understand 75% of the text in a language. Vocabulary flashcards (preferably with audio) can help make some very simple dialogues or stories comprehensible at the beginning but flashcards are not enough for learning a language.