Walked is a verb.
Yesterday is a noun in that sentence.
The word yesterday is an adverb.
"Yesterday" is an adverb modifying the noun "afternoon".
Yesterday is an adverb in that sentence.
It's an adverb.
I think yesterday is a noun, because it is definitley not a verb or adjective. It is not an action and it does not describe anything.
In the sentence "yesterday the leaves hung on the tree," "yesterday" is functioning as an adverb modifying the verb "hung."
A noun.
Park is a noun in that sentence.
"Yesterday" can be an adverb, a noun, or an adjective.ExamplesAdverb: We arrived yesterday.Noun: Yesterday started well. All our yesterdays.Adjective: Yesterday morning
Yesterday he paddled his canoe out into the lake and camped on an island overnight.
As it is the name of place, then it is a proper noun.