Final answer:
The words ágil and agile are cognates. Cognates are words from different languages resembling each other in spelling, pronunciation, and meaning, often with a shared etymology. They are neither affixes, root words, nor borrowings.
Step-by-step explanation:
The words ágil and agile are examples of cognates. Cognates are words in different languages that have a similar spelling, pronunciation, and meaning, and usually share a common etymological origin. For instance, the Latin root 'agilis' has given rise to the English 'agile' and the Spanish 'ágil', which both describe something or someone capable of moving quickly and easily. These words are not affixes, which are elements added to the beginning or end of a root word to alter its meaning, nor are they root words, which serve as the base part of a longer word. While they might be considered borrowings by one language from another, the term 'cognates' specifically refers to their common heritage and parallels in multiple languages.