Muggles' Guide to Harry Potter/Magic/Specialis Revelio

Overview
Specialis Revelio is a charm used to reveal hidden ink.

Extended Description
In Harry Potter and the Half-Blood Prince, Hermione Granger uses it on the Half-Blood Prince's copy of Advanced Potion-Making.

Analysis
It seems as if the first word of the spell, Specialis, does not need to be stated for the spell to be used.