What tool is a type of context clue you could use to determine the meaning an unfamiliar word?

The tool that's a type of context clue you could use to determine the meaning of an unfamiliar word is called a synonym.

Here's why:

* Synonym: A synonym is a word that has the same or nearly the same meaning as another word. When a text uses a synonym for an unfamiliar word, it's a clue to help you understand its meaning.

For example:

* "The arduous climb was a challenge, but they persevered."

* "The difficult climb was a challenge, but they persevered."

Here, "arduous" is the unfamiliar word, and "difficult" is the synonym that provides a clue to its meaning.