Let's say Pat is an English speaker who has a strong understanding of its history and root words, but has never seen or heard of a hippopotamus until reading your comment. Without looking the word up, Pat can break down the word into the Greek roots híppos (horse) and potamós (river). From these roots, Pat can assume that a hippopotamus is a "river horse" -- a four-legged animal, probably a large mammal, that lives in or around rivers.

Let's say Jordan is a practiced speaker of Toki Pona who has never seen a hippopotamus, and has just now heard "river wonder dog" for the first time ever. Just like Pat, Jordan can infer that this refers to a four-legged animal, probably a mammal, definitely big or impressive, that spends lots of time in water. (The context of rivers is lost, so Jordan might assume that this creature lives on ocean shorelines, or even in open water.)

In either language, the creature's name uniquely identifies it to people who are already familiar with the animal, and gives a useful description to people who are unfamiliar with it.

This is actually really common in languages. Like the other commenter noted in Chinese. I'll give another example. Bear(熊) + cat(猫) = panda(熊猫). There's tons of these that don't make sense unless you already know. There are also plenty that you might be able to put together with context (electric + brain = computer). But we can go into any language and find things like this. The article mentions "microscope" which is already a compound word in English[0]. German has "sick wagon" for "ambulance" and "finger shoes" for "gloves". French has "animal companion" as "pet".

I'll also mention that German and Mandarin have a significant amount of compound words. There's even a joke about German, that if you want to make a new word you just smash two words together. Animal that lives in my house? House-animal. Haustier (pet).

[0] English is a "bastardization" of a bunch of languages. There's plenty of words in it that are compound words from other languages.

Others address that this is not uncommon in languages, nor is it unhelpful even if you don't know.

But for a different counterpoint, lets say we gave a specific name to everything. For example, in my new, totally not-fake language, a hippo is a klantomolarnal.

Unless you already know a hippopotamus is a klantomolarnal, when someone says klantomolarnal, will you know what he means?

So, if our options are:

1) colloquial compound words that are informative but inexact and may require context (most languages) 2) unique words for everything with no intrinsic meaning (no language) 3) compound words that uniquely describe a thing (ithkuil, lojban, basically nothing useable)

It seems clear that (1) is our only real option. Toki Pona just has a harder time because of the smaller shared vocabulary which makes things more ambiguous.

In my limited experience, context clears things up tremendously.

(incoming rusty toki pona)

o sina lukin e ni! // Look at that!

o sina lukin e telo suli soweli! // Look at that big, water mammal [hippopotamus]!

Your second sentence would probably be "o sina lukin e soweli suli pi telo". what you wrote is more like "big animal water".

Like many languages, you'd have to learn more than the base vocabulary. If you were learning Chinese, could you guess what an electric brain (diànnǎo, 电脑), a vertical rise machine (zhíshēngjī, 直升机) or a cat head eagle (māotóuyīng, 猫头鹰) was? Maybe not, which is why you'd learn the Chinese for computer, helicopter, and owl.

This is how many languages works, but the spirit of Toki Pona is genuinely different (though many learners come in with the impression). Learning compound phrases won't really help you much.

One could say that the idea is to, if you have to refer to something in a given context, you try to cobble together a description, just enough to differentiate it from other things. "sike tu" (two circles) will be useful to differentiate a bicycle from a car, but if you want to differentiate them from a pair glasses you'll probably need to use a different term - "sike tawa" (moving circles) maybe! What you have to learn, instead of set compound phrases, is the ability to improvise names/descriptions for things on the fly :)