in words from Arabic (or assumed to be), it is the definite article "the." Sometimes rendered in English as el-. Often assimilated to following consonants (as-, az-, ar-, am-, an-, etc.). Examples include almanac, alchemy, alcohol, algebra.
akin
Akita
Akkadian
Akron
*akwa-
al-
*al-
-al
al dente
al fresco
al Qaeda