A small circle
ْ written above a letter in Arabic
to indicate that there is no following vowel. Words rarely end with consonant
s in Arabic, and when they do they often take on a linking
vowel when another word comes after them, so the main use of sukûn
is in consonant cluster
In Unicode: sukûn is &1618;. Here is the word sukûn itself as an example:
A similar device in Sanskrit is the mark virama.