Appoggiatura -

Example : An appoggiatura on a quarter note results in two eighth notes.

: Unlike the acciaccatura (short grace note), the appoggiatura does not have a diagonal slash through its stem. appoggiatura

: For dotted notes, the ornament typically takes two-thirds of the value. Example : An appoggiatura on a quarter note

The amount of time "stolen" from the principal note depends on the note's original duration and musical style: appoggiatura

which is sometimes referred rather confusingly by Arban ... - Facebook