The old man was tired of walking. The underlined word in the sentence is used as a :

Question

Accepted Answer

The underlined word "walking" is used as a **Gerund** in the sentence "The old man was tired of walking." Here's why:

*   **Why Option 2 (Gerund) is correct:** A gerund is a verb form ending in "-ing" that functions as a noun. In this sentence, "walking" is the object of the preposition "of." The preposition "of" requires a noun or noun equivalent as its object, and "walking" fulfills this role. The entire phrase "of walking" acts as a prepositional phrase modifying "tired." Therefore, "walking" is functioning as a noun, making it a gerund.

*   **Why Option 1 (Participle) is incorrect:** A participle is a verb form that can function as an adjective or part of a verb phrase. While participles also end in "-ing," they modify nouns or form continuous verb tenses. In this sentence, "walking" is not modifying a noun, nor is it part of a continuous verb tense. It's acting as the object of the preposition.

*   **Why Option 3 (Noun) is incorrect:** While a gerund *functions* as a noun, it's specifically a *verbal noun*. Calling it simply a "noun" is not precise enough. The term "gerund" captures the fact that it's derived from a verb and retains some verbal characteristics (e.g., it can take objects or be modified by adverbs, though not in this particular sentence). While technically a gerund *is* a type of noun, the option "gerund" is more specific and accurate in this context.

*   **Why Option 4 (Adverb) is incorrect:** An adverb modifies a verb, adjective, or another adverb. "Walking" does not modify any of these in the sentence. It's not describing how the old man was tired; it's the *reason* for his tiredness, expressed as the object of the preposition "of."