1. In theory; according to the assumed facts 
2. In a theoretical manner
   "he worked the problem out theoretically"

See also: theoretical

Antonym: empirically

• attemper
• attempt
• attempted
• attempter
• attend
• attend to
• attendance
• attendance check
• attendant
• attended
• attendee
• attender
• attending
• attention
• attention deficit disorder
• attention deficit hyperactivity disorder
• attention span
• attention-getting
• attentional
• attentive
• attentively
• attentiveness
• attenuate
• attenuated
• attenuation