Yes.
Nightmare formerly meant an evil spirit that was supposed to harass or suffocate sleeping people. The word came from two words -- night + Old English mare, which meant an evil spirit. In the late 13th century it meant an evil female spirit afflicting sleepers with a feeling of suffocation.
Mare with this meaning is now obsolete in English
"Airplane pilot" is an example of a compound idea noun where two words come together to form a single concept.
A noun, of the abstract type.
Yes. night + mare = nightmare
No, it is not a verb. Nightmare is a noun (bad dream).
Yes, "nightmare" is a common noun because it refers to a general type of experience or feeling that anyone can have.
Yes, the word 'nightmare' is a noun, a word for a frightening dream; a frightening or horrible experience; a word for a thing.
what is a compound noun?
No, "online" is a closed compound word, not a compound noun.
A compound noun form of the noun 'bride' is bridegroom.
Nightmare is a noun. Nightmarish is the adjective form. Nightmarishly is the adverb form.
Is the word coat a compound noun?
A compound noun is a noun that consists of two or more words, usually separated by dashes. The word caterpillar is not a compound noun.