What does the root word platy mean?

The root word "platy" comes from the Greek word "platys", which means flat or broad.

This root is commonly found in words related to:

* Flatness: Platypus (a flat-billed mammal), platyhelminthes (flatworms)

* Width: Platycephalidae (flatheads, a family of fish), platycnemism (having flat shins)

* Spread: Platycerium (staghorn ferns, which have flat, broad fronds)

So, whenever you see the word "platy" in a word, it usually refers to something that is flat, broad, or spread out.