Interjectors are words and phrases that express an emotion or sentiment on the part of the speaker.
Interjector is a grammatical function.
The grammatical form that can function as the interjector in English grammar is the interjection. Other grammatical forms may also perform the function of interjector.
Interjectors are not constituents of the subject or the predicate. Interjectors are also not grammatically-related to any other part of the sentence.
Brinton, Laurel J. & Donna M. Brinton. 2010. The linguistic structure of Modern English, 2nd edn. Amsterdam: John Benjamins Publishing Company.
Hopper, Paul J. 1999. A short course in grammar. New York: W. W. Norton & Company.
Huddleston, Rodney. 1984. Introduction to the grammar of English. Cambridge: Cambridge University Press.