Like trills, they can be chromatically modified by a small flat, sharp or natural accidental.
The term entered English musical terminology at the beginning of the 19th century, from the German Mordent and its Italian etymon, mordente, both used in the 18th century to describe this musical figure.
The same applies to trills, which in Baroque and Classical times would typically begin with the added, upper note.
Practice, notation, and nomenclature vary widely for all of these ornaments, and this article as a whole addresses an approximate nineteenth-century standard.
The slide can be written using a symbol similar to that of the mordent, but placed to the left of the principal note, rather than above it.