If you’ve been paying attention to Silicon Valley this year, you’ve likely heard of a startup unicorn. (If you haven’t, read our cover story, The Age of Unicorns, from January.) The proliferation of these billion-dollar startups has created its own vocabulary. Here’s our guide to speaking the language.

One-on-One Deal: A $100 million round of funding with a $1 billion valuation.

My Little Pony: A startup worth $10 million or more. (Coined by Dave McClure, founder of accelerator program 500 startups.)

Centaur: A startup worth $100 million or more.

Decacorn: A startup worth $10 billion or more.

Quinquagintacorn: A startup worth $50 billion or more (see Uber).

Unicorpse: A former unicorn, now valued at less than $1 billion.

*Honest, we didn’t make these up.

To see our full unicorn list, click here.

A version of this article appears in the September 15, 2015 issue of Fortune magazine with the headline “Not all unicorns are created equal.”