If you need to add a word to the dictionary, it's pretty clear where it goes. The dictionary is a handy reminder of how taxonomies work. The words aren't sorted by length, or frequency or date of first usage. They're sorted by how they're spelled. This makes it easy to find and organize.
The alphabet is an arbitrary taxonomy, without a lot of wisdom built in (are the letters in that order because of the song?).
It's way more useful to consider taxonomies that are based on content or usage.
Almost everything we understand is sorted into some sort of taxonomy. Foods, for example: we understand intuitively that chard is close to spinach, not chicken, even though the first two letters are the same.
The taxonomy of food helps you figure out what to eat next, because you understand what might be a replacement for what's not available.
Shopify has more in common with Udemy (both tech startups) than it does with the Bank of Canada (both based in Ottawa).
Your job, if you want to explain a field, if you want to understand it, if you want to change it, is to begin with the taxonomy of how it's explained and understood.
Once you understand a taxonomy, you've got a chance to re-organize it in a way that is even more useful.
Too often, we get lazy and put unrelated bullet points next to each other, or organize in order of invention. For example, we teach high school biology before (and separate from) chemistry, even though you can't understand biology without chemistry (and you can certainly understand chemistry without biology). We do this because we started working on biology thousands of years before we got smart about chemistry, and the order stuck.
The reason an entrepreneur needs a taxonomy is that she can find the holes, and figure out how to fill them.
And a teacher needs one, because creating a mental model is the critical first step in understanding how the world works.
If you can't build a taxonomy for your area of expertise, then you're not an expert in it.