slaka bu BY* cmavo cluster

letteral: Lojban "," character.

On affix form:

slaka
x1 is a syllable in language x2.

In definition:

lerfu
x1 (la'e zo BY/word-bu) is a letter/digit/symbol in alphabet/character-set x2 representing x3.

In notes:

sance
x1 is sound produced/emitted by x2.
valsi
x1 is a word meaning/causing x2 in language x3; (adjective: x1 is lexical/verbal).