# quid pro quo

idiom · CEFR C1

Source: https://englishreference.com/idiom/quid-pro-quo
Updated: 2026-08-03

## Meaning

Something given in return for something else, usually as an understood trade.

## Examples

- I'll cover your shift, but there's a quid pro quo.
- The support was offered without conditions, though everyone understood the quid pro quo.
- No quid pro quo was ever stated, which is the entire difficulty with proving one: the arrangement consisted of two decisions taken four months apart by people who had had lunch in between.

## Origin

The phrase started in the pharmacy. Quid pro quo — this for that — was the medieval apothecary's term for substituting one ingredient for another when the prescribed one was unavailable. It could be perfectly legitimate and it could kill you, and the earliest English uses carry that unease: a quid pro quo was something passed off in place of the real thing. By the sixteenth century the sense had shifted to a fair exchange, and Roman legal thinking underlies where it went next. Contract in Roman law turned on reciprocity — an obligation that ran only one way was hard to enforce — and English law developed its own version of the requirement, which is why the phrase settled so comfortably into legal English. Its modern flavour is transactional and slightly compromising. A quid pro quo is rarely a purchase; it is a favour with an unspoken invoice attached.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.