Appose is a word adopted in English language from the Latin diction. Moreover, an appositive is referred to as noun phrase which elaborates the meaning of the noun in the same sentence.
Proper punctuation must be utilized with appositive phrases. Any defining appositive phrase is separated with the help of commas. It can be used in the beginning, or in the middle, or at the end of the sentence. It is necessary to use commas as a separator to form a relationship with the subject, within the statement.
Example: Harry Potter, a gifted scholar, is Professor McOnigall's favorite.
However, in the asked query, appositive is carried in the first sentence, that is, "You must be home by eight o'clock your curfew time." The absence of comma breaks the structure and flow of the sentence. If we write- "You must be home by eight o'clock, your curfew time," this in return explains the importance of the phrase- "your curfew time". Else it seems useless in the statement.
