Other forms: exoplanets
An exoplanet is a planet that revolves around a different sun than ours. Sometimes a pizza takes so long to be delivered, you think it must be coming from one of the furthest known exoplanets!
In the 1970s, when space science was taking off, the word exoplanet was invented by attaching the combining form exo-, meaning "outside," to the word planet. That English form exo- comes from the Greek, also meaning "outside," and is used in this case because the planet is outside our solar system. Exoskeleton is another word that uses this combining form, and refers to the hard supporting structure found on the outside of certain animals such as insects and crabs.