‘Yī bǐ’ literally means ‘one stroke’—combining the numeral 一 (yī, ‘one’) and 笔 (bǐ, ‘brushstroke’ or ‘pen stroke’). In writing and calligraphy, it refers to a single, continuous movement of the brush or pen, such as the horizontal stroke in the character 一 itself. This meaning extends metaphorically to ‘one transaction’ or ‘one item’ in financial or administrative contexts, where each entry in an account is treated as a discrete unit—like a single stroke on a ledger.

The phrase emphasizes singularity and completeness: whether describing the elegance of a single calligraphic line or the clarity of recording one sale or expense, ‘yī bǐ’ conveys that this is a self-contained, indivisible unit of action or record. It’s commonly used in banking, accounting, and everyday conversation about money or documents—e.g., ‘a一笔 deal’, ‘a一笔支出’, or ‘a一笔账’.