Mainly adv. : Very strongly; mightily; to a great degree.

Mainly adv. : Principally; chiefly.

Example:
What breed cow is Mainly used for milking and has a realy good temperment?

Taxonomy
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Defination from the web:
mainly from the Merriam-Webster Online Dictionary with audio pronunciations, thesaurus, Word of the Day, and word games. ... Learn more about "mainly" and related topics at Britannica.com. See a map of "mainly" in the Visual Thesaurus. Pronunciation Symbols. Share this entry: ...