1. According to need (physicians use PRN in writing prescriptions)
   - as needed, as required, PRN

Encyclopedia: Pro re nata

• attar of roses
• 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