The most frequently used and easily identifiable is the Symbol of the Horned Rat, which signifies not only the deity of the Skaven but also the Skaven race as a whole.
The Skaven alphabet is comprised of 13 letters, approximated in a Latin-based writing system as 8 consonants, 4 vowels, and the 13th letter, "X", which primarily serves as an unvoiced mutation.
Skaven letter-runes are represented by both a Formal and Informal symbol. While its tempting to compare these to upper and lower-cases in English, their application in Skaven writing is nowhere near as consistent. Though it is standard practice that any nouns (proper or otherwise) are begun with a Formal letter, beyond that both symbols are used pretty much interchangeably, seemingly at whim.
Another peculiarity of Skaven writing is that, in the case of nouns where a commonly used pictographic symbol already exists, the rune commonly replaces the first letter of the word when written out. This is also the case insofar as when the names of Skaven personages are written out, the first letter is often replaced with the symbol for their clan.
The following guide provides the closest English equivalents of the Skaven letter rune phones. The structure of the Skaven mouth produces a variety of sounds generally foreign to human speech. Just as there are a number of palatal and palatal-alveolar phones used by the Skaven that humans can, at best, only approximate, Skaven themselves are unable to accurately reproduce the common English labials (p, b, m, w). Much like a ventriloquist, the Skaven must resort to approximations, often by way of labio-dentals.
As a general rule of thumb, Skaven vocalizations are higher pitched than English is typically spoken, & most consonants are palatalized, giving the tongue a guttural inflection.