What does an inflectional ending do to a word?

The assertion that an inflectional ending alters the meaning of a word captures the essential function of inflectional morphemes. Inflectional endings are linguistic elements added to a base word to express different grammatical categories such as tense, mood, aspect, person, number, or gender. For instance, adding the inflectional ending "-s" to the noun "cat" changes its meaning from singular "cat" to plural "cats," thus altering the reference of the word to indicate more than one. This modification in meaning is intrinsic to the grammatical structure of language, allowing for nuanced communication.

In contrast, the other options misrepresent the nature of inflectional endings. Changing the original root word completely suggests a transformation that creates a new lexeme, which is not typical of inflectional morphology. Also, creating an entirely different word implies a more significant morphological change, as seen with derivational morphemes, rather than the grammatical adjustments made by inflection. Lastly, simply adding length to a word does not encompass the functional aspect of altering meaning; while inflectional endings may lengthen words, their primary role is to adjust grammatical properties rather than merely extend word forms.