Mortal Seeming
In the common Parlance of the Kithain, the Mortal Seeming is the mortal appearance of a changeling. This is how mortals perceive the fae.
Overview

To survive in the mundane world, the Kithain have had to adopt the appearance of humans; to protect themselves from the forces of disbelief. These facades protect the fae but hints of who they really are always slip through. A Boggan may be short, rotund, or have a large nose Eshu tend to have an African or Middle Eastern look. Nockers may be thin with expressive eyebrows and pale complexions. Pooka will have features reminiscent of their animal form, perhaps a hooked nose or hair that hangs like cocker spaniel ears. A Redcap will have mottled skin and bad teeth or piercings. Satyrs will be hairy and wild, Sidhe elegant, thin, and ethereal. Sluagh will be pale and thin and quiet. Trolls tend to be tall. In some cases the slippage can be so great as to be a flaw. Having horns or blueish skin or pointy ears can be a problem.
As Changelings age, their mortal seemings change naturally. Children hit puberty, become adults, age, grow frail, and die. While being in a freehold can halt that progression, remaining there courts disaster in the form of Bedlam. Because this means the fae age more slowly than their peers, many childlings and wilders often run away from home before people begin to ask questions. Even grumps can become noticeable after years of not aging the way their peers and coworkers do.
For more on how Changelings age, see the article Changeling.
References
- CTD: Changeling: The Dreaming Second Edition, p. 8, 65-66