Explanation
"I worked morning till noon."
"Till" is a preposition because it shows the relationship between "morning" and "noon" (expressing time).
Noun – "Till" is not a person, place, or thing.
Conjunction – "Till" can sometimes be a conjunction, but here it does not connect two clauses.
Verb – "Till" can mean "to prepare land for farming," but not in this context.
Adverb – It does not modify a verb, adjective, or another adverb.
