1. <programming, compiler> Extra information associated with a
particular point in a document or program. Annotations may be
added either by a compiler or by the programmer. They are
not usually essential to the correct function of the program
but give hints to improve performance.
2. <hypertext> A new commentary node linked to an existing
node. If readers, as well as authors, can annotate nodes,
then they can immediately provide feedback if the information
is misleading, out of date or plain wrong.
