Final answer:
The word 'today' in the sentence is an adverbial noun that indicates time, but it is not traditionally an adjective or adverb. The word 'lot' is a noun indicating quantity and is often mistaken for an adjective.
Step-by-step explanation:
In the sentence "There were a lot of dogs in the dog park today," the word that is either an adjective or an adverb is today. However, 'today' functions as a noun in this context, specifically an adverbial noun, which can sometimes be confused with an adverb because it indicates time. The word 'lot' is a noun that refers to the quantity or the number of dogs, while 'dogs' and 'park' are both nouns, referring to the animal and the public space respectively.
Adjectives and adverbs are words that describe or modify other words in a sentence. Adjectives describe nouns or pronouns, giving more information about their quality, quantity, or other characteristics. Adverbs typically modify verbs, adjectives, or other adverbs, providing more detail on how, when, where, or to what extent an action is performed.