ptilosis

Borrowed from New Latin ptilōsis, from the Ancient Greek πτῐ́λωσῐς (ptílōsis).

ptilosis (usually uncountable, plural ptiloses)

1. (ornithology) The appearance or study of feathers on a bird, including factors such as their texture or shape.
   • 2013, Donald S. Farner, Avian Biology‎, volume 2, page 31:

     Pterylography must be based on the distribution of the follicles, for the ptilosis as seen externally does not reflect the actual pterylosis.

2. (medicine) Loss of the eyelashes, due to ulceration or other damage to the follicles.
   • 1826, The Lancet - Volume 10, page 323:

     The state of the lid, when deprived of the eyelashes, has been called ptilosis or alopecia ; the effect of the removal is very inconsiderable, and unless you look closely to the lid of a person of light hair, you can hardly distinguish whether the eyelashes are wanting or not.

   • 1836, London Medical and Surgical Journal - Volumes 8-9, page 677:

     This is an aggravated form of the last disease, and presents ulceration and induration of the edges of the eye: lids, so as to cause the cilia, or lashes to fall out—ptilosis.

   • 1843, Sir William Lawrence, Isaac Hays, A Treatise on the Diseases of the Eye, page 124:

     Loss of the eye-lashes, (ptilosis, madarosis, alopecia.) -- Destruction of the bulbs by ulceration or by injury causes permanent loss of the cilia, which may be either total or partial.

   • 2012, Kenneth C. Chern, Michael A. Saidel, Ophthalmology Review Manual, →ISBN:

     There may be ulceration and notching (ptilosis) of the lid margin (Figure 1.3).

In ornithology, ptilosis refers to the properties of the feathers themselves, while pterylosis refers to the arrangement of those feathers and how they are implanted in the skin.

In medicine, ptilosis refers specifically to the eyelashes, while madarosis can also apply to the eyebrows, and alopecia can apply to hair loss in any part of the body.

• (properties of feathers): pterylosis
• (loss of eyebrows): alopecia, madarosis