Mainstay is a noun.
Fruits and vegetables are the mainstay of a healthy diet. Diary products of a mainstay of Wisconsin's economy.
Oil is the mainstay of Saudi Arabia's economy.The sailor used the mainstay to secure the mainmast forward.
part of speech
The part of speech for this particular word is a noun.
The word "mainstay" is a noun. An example of a sentence containing the word would be: Tourism is the mainstay of this small harbor town.
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "explicit" is an adjective.
The part of speech for "twirl" is a verb.
The part of speech for "unfamiliar" is an adjective.
The part of speech of "came" is a verb.