Accidentals

noun

1. A property which is not essential; a nonessential; anything happening accidentally.
2. Those fortuitous effects produced by luminous rays falling on certain objects so that some parts stand forth in abnormal brightness and other parts are cast into a deep shadow.
3. A sharp, flat, or natural, occurring not at the commencement of a piece of music as the signature, but before a particular note.
4. Part of a text that has a mainly structural purpose, such as spelling, punctuation or capitalization.