Is the form of the following list correct?
Definition of insomnia：
１. Hard to fall asleep
２. Easy to wake up
３. Wake up too early
Which is acceptable, 'Definitions of insomnia' or 'Definition of insomnia'?
Both could be correct. It depends on the context. If you only have one definition, us definition. For more than one, use definitions. A definition of a man is male. Some definitions of a man are: a male, a primate, and a biped.