*pelə-, *pla-

The core idea of the family was:

flat, spreading out

This theme is pretty visible in offspring like flat, plain, plateau, platter or field but there are loads more relatives that make sense once you know about them.

Here’s a little overview over English:

• flat
• field (flat surface)
• plane (a flat surface, the idea of “airplane” comes from a French word that’s also related)
• plateau (flat surface, but it’s in French)
• Poland (Based on the Slavic word “pole” for “field”)
• plan (a plane surface to draw your plan on)
• plate, platter 
• platform
• place (wide open space)
• plant (original sense was flattening the ground to sow)
• transplant (originally “put down elsewhere, from the sense of planting/sowing)
• implant (“put in”)
• supplant (“put in something different”)
• platypus (Literally: “flat feet” in Greek)
• plasma (Originally “spreading thin”)
• plastic (Started from the idea of plasma and focused on being moldable)