What is the natural size and shape of the eyebrow, and what are the boundaries of the eyebrow from which hair should be thinned without affecting the original hair, especially the hair parallel to the eye and the hair on the forehead?

It is permissible to thin the eyebrows if they are unusually thick or long, disfiguring one's appearance, and this should be done only to the extent that removes the disfigurement. As for the hair between the eyebrows, there is no harm in removing it, especially if it disfigures one's appearance; this should be done by shaving, not plucking. The hair that is level with the eye falls under the same ruling as the eyebrows, unless it is outside the eyebrows, in which case there is no harm in removing it. Removing eyebrow hair by plucking is forbidden and is considered a major sin (al-namṣ). As for trimming or shaving it, there is a difference of opinion, and it is better to avoid it. Removing unusual hair in places where it is not customary for hair to grow (such as a mustache or cheek hair) is permissible because it is disfiguring.