AMEN

int. & n.

--int.

1. uttered at the end of a prayer or hymn etc., meaning 'so be it'.

2 (foll. by to) expressing agreement or assent (amen to that).

--n. an utterance of 'amen' (sense 1).

Etymology: ME f. eccl.L f. Gk f. Heb. ' amen certainly