Final answer:
The abbreviation that might be used on a prescription for a medication amount that varies day to day is 'prn', which stands for 'as needed'. The pharmacy technician will need to calculate the final amount needed to fill the prescription.
Step-by-step explanation:
The abbreviation that might be used on a prescription for a medication amount that varies day to day is prn. This abbreviation stands for 'pro re nata', which means 'as needed'. When a prescription includes 'prn', it indicates that the patient should take the medication only when necessary, and the pharmacy technician will need to calculate the final amount needed to fill the prescription based on the patient's needs.