Final answer:
In medical shorthand, the letter 's' with a line over it represents the term 'without', derived from the Latin term 'sine'.
Step-by-step explanation:
The letter s with a line over it is a medical abbreviation that stands for without.
The shorthand notations using a line over letters originate from Latin terms used in prescriptions. In Latin, 'sine' means 'without,' and is abbreviated as 's' with a bar (or line) over it in medical prescriptions and notes.