When describing hunting rifles of the 17th, 18th and 19th century, some writers use the term flintlock, instead of using the fuller description of flintlock mechanism.
The flintlock was a primitive gun.
flintlock
Yes, as long as you use the word to describe another word in the sentence, original is an adjective. For example, in the sentence "This is an original painting by van Gogh." the word "original" is an adjective. If, however you use the word to describe the entire item as in "This is an original.", it is a noun.
This question is very original.
Please explain the relevance of your complaint.
Conservatism is the original American way.There's one for you.
That was indeed the original document.
This model must conform to the original design.
I had a premonition that I would answer this question. (Tell your teacher you DID use "premonition" in a sentence in your original question).
Here is a sentence that uses the word metonymy. Metonymy is a figure of speech that replaces one word for another.
A sentence does not have a root word. A root word is the main or original portion of most words. For example, the root of discrimination is the word " crime ". Perhaps you mean the key idea of your sentence ?
I censure the dog for knocking over the vase.