root word
root word (raíz)
the main part of a word that carries its basic meaning, to which prefixes and suffixes are added.
Example
The clerk was unhelpful. (Unhelpful = un- + help + -ful; help is the root word.)
In Spanish
root word (raíz) — la parte principal de una palabra, que lleva su significado básico y a la que se añaden prefijos y sufijos.
The clerk was unhelpful. (Unhelpful = un- + help + -ful; help es la raíz.)