What does "half-eaten" mean?
"Half-eaten" is an adjective that describes food which is partially consumed or has already been eaten from. The purpose of the hyphen here is to connect two words which act as a single idea and modify the noun they are describing. So you can definitely understand this as "half-" + a past particle, and you can add many different past particles to "half-" to create new words. Ex: A half-cooked piece of chicken Ex: A half-watered plant