Which term defines a base word altered with a suffix to indicate tense?

The correct term for a base word altered with a suffix to indicate tense is indeed an inflectional suffix. Inflectional suffixes are added to the end of a base word (the root) to modify its tense, number, aspect, mood, or voice. For example, adding "-ed" to the verb "walk" changes it to "walked," indicating past tense.

This process is a key aspect of language that allows for the modification of verbs to provide additional information about time. In contrast, a derivational prefix is used to create a new word by changing its meaning, rather than altering its tense. Compound words involve the combination of two or more whole words to create a new word entirely, such as "toothbrush." A root word refers to the core part of a word, which could stand alone or be modified with affixes but does not specifically describe the alteration of tense through a suffix.

In summary, inflectional suffixes play a significant role in grammar by providing necessary tense information, making them essential for proper sentence structure and meaning.