Bible Dictionaries
Amen

Webster's Dictionary

(1):

(interj., adv., & n.) An expression used at the end of prayers, and meaning, So be it. At the end of a creed, it is a solemn asseveration of belief. When it introduces a declaration, it is equivalent to truly, verily.

(2):

(v. t.) To say Amen to; to sanction fully.

Bibliography Information
Webster, Noah. Entry for 'Amen'. Noah Webster's American Dictionary. https://www.studylight.org/​dictionaries/​eng/​web/​a/amen.html. 1828.