Chiasmus is a literary structure in which parallel terms or concepts are first introduced in order and then again in reverse order to make a point, often emphasizing the middle concept which either appears twice in succession (ABB'A') or only once (ABCB'A'). It takes its name from the from the Greek letter ? (chi), and is also called chiasm or chiastic structure.
A. to the end that we should be to the praise of his glory, B. we who had before hoped in Christ: C. in whom you also, having heard D. the word of the truth, D'. the gospel of your salvation, C'.in whom you also, having believed, B'. you were sealed with the Holy Spirit of promise, which is an earnest of our inheritance, A. to the redemption of Gods own possession, to the praise of his glory.