Pronounced "RAY‐fee." The narrow ridge or seam running the length of the ventral side of the penis, beginning at the frenulum, and extending down the distal side of the penis, through the mid-line of the scrotum, across the perineum, ending at the anus. It generally has a different color than the adjacent skin, and forms a noticeable line on the scrotum.

The raphe is the result of a fetal developmental phenomenon where the scrotum (the developmental equivalent of the labia in females) and penis close toward the midline and fuse under the influence of testosterone.

Image Source: www.en.wikipedia.org/wiki/File:Scrotum2.jpg