best

best is an Adverb

Definition:

[1] Having good qualities in the highest degree; most good, kind, desirable, suitable, etc.; most excellent; as, the best man; the best road; the best cloth; the best abilities. When he is best, he is a little worse than a man. Shak. Heaven`s last, best gift, my ever new delight. Milton.

[2] Most advanced; most correct or complete; as, the best scholar; the best view of a subject.

[3] Most; largest; as, the best part of a week. Best man, the only or principal groomsman at a wedding ceremony.