Sauce is a liquid or semi-liquid served with food: "He poured the sauce over the pasta." Source is the origin of something — a river's start, a supplier, a person providing information: "The journalist protected her source." The word meaning origin has an r in it; the food does not.
The core difference
Sauce is a food word and nothing else. Source is about where something begins or comes from, and it also works as a verb meaning to obtain from a particular place.
In many accents the two are close enough to cause trouble. In non-rhotic British speech, where the r in source is not pronounced as a consonant, the pair can sound nearly or entirely identical. In rhotic accents — most of North America, Ireland, Scotland — the r is audible and the words are clearly distinct. If your accent merges them, you cannot rely on your ear; you have to check the meaning.
How to use each
- Sauce — "The chilli sauce was hotter than expected." "Reduce the sauce for another five minutes."
- Source (noun) — "Sunlight is our main source of vitamin D." "The Thames has its source in Gloucestershire." "Two sources confirmed the story."
- Source (verb) — "We source our beans directly from growers." "The parts were sourced locally."
The test
Substitute origin or supplier. If either fits, the word is source: "our main origin of vitamin D" is clumsy but comprehensible, which tells you it is source. If you could instead substitute gravy, dressing or ketchup, it is sauce.
For spelling, tie the r to origin — both contain an r, and both are about where something starts. Sauce, with no r, stays on the plate.
Compounds that fix the spelling
Some phrases are effectively locked: open-source software, source code, primary source, a reliable source, outsource. On the other side: soy sauce, white sauce, apple sauce, saucepan, saucer. Noticing that saucepan and saucer both belong to the kitchen helps anchor the shorter spelling.
The extra sense of sauce
In British English, sauce can also mean cheek or impudence — "None of your sauce" — with the adjective saucy meaning either cheeky or mildly risqué. That sense is informal and dated, but it explains why saucy never means anything to do with origins.
The mistake people actually make
The commonest written slip is "a reliable sauce" or "we sauce our ingredients locally" — an error a spellchecker will never flag, because both spellings are real words. Search your own drafts for sauce if you write about suppliers, references or citations; a single missed r changes a supply-chain claim into a condiment.
Frequently Asked Questions
Is it "sauce code" or "source code"?
Source code. It refers to the original human-readable text of a program — its origin, before compiling. "Sauce code" only appears as a joke or a typo.
Do sauce and source sound the same?
In non-rhotic accents such as standard southern British English they can sound identical or nearly so, because the r is not pronounced as a consonant. In rhotic accents, including most American ones, the r is clearly audible and the words differ.
Can source be a verb?
Yes. To source something is to obtain it from a particular place: "We source our wool from Yorkshire." Sauce is not used as a verb in ordinary writing.