Chinese characters aren't what speakers of Western languages would consider "words". Like English words, they are symbols combining both meaning and pronunciation (one or slightly more of each), so sometimes they are like English words, but more often they are used in fixed combinations with each other making them more like roots and affixes (prefixes, infixes, suffixes).

Chinese characters are more like the four components of the word "nonbiological" (non, bio, logos, al) than like the word "nonbiological" itself but, unlike English, there are more cases where the components can also stand alone.

Ten thousand is on the high side for the number of characters an educated, native Chinese speaker would usually know (much less use), but the number of what Westerners might consider "words" known by such a Chinese speaker would typically be much higher than 10,000, with most of them being composites of multiple characters.

In practice, the Chinese language typically represents concepts in 2 or 4 ideograph segments. Not every possible combination is in regular usage, but the number of potential linguistic "words" is closer in order of magnitude to the 10000 choose 2 binomial coefficient, i.e. 49995000.

So basically when they don't have a word for a new concept they devise a new one made of existing radical+ideograph+ideograph.