A commissure; an intersection or crossing of two tracts; especially, the optic commissure, or crucial union of the optic nerves.

an intersection or crossing of two tracts in the form of the letter X

cross-shaped (the Greek letter chi is cross-shaped) (P)

GR A rhetorical device used in ancient writings, including Biblical Greek, in which key words in a phrase, verse, or series of verses is repeated in an inverse pattern. It is sometimes called "inverse parallelism." This device takes its name from the Greek letter chi, (X), because it has a structure that resembles the letter 'X.' The repeated elements are often designated with letter and superscripts, such as A, A'; B,B', and so on.. In a chiasm, these elements are related to each other in parallels so that the first and the last are parallel, the second and the second from the last are also parallel, and so on. There can be two or more elements. The device is generally used to draw attention to the repeated words, to give them a special emphasis. The repeated words or phrases - while they may differ slightly in grammatical or syntactic form - always exhibit the same meaning. An example of chiasm is the familiar saying of Jesus: "The first shall be last and the last shall be first." The chiasm is: "first...last ; last...first," forming the pattern, AB B'A'. The structure can be extended to include many repeated elements in complex patterns, stretching over many verses.

a form of parallel, the only distinction being the direction in which the matching sequence flows