Quality is how good something is, or a characteristic it has: <em>The build quality is excellent.</em> Quantity is how much or how many there are: <em>We ordered a large quantity of paper.</em> Quality answers "what is it like?"; quantity answers "how much?" — you can have a huge quantity of terrible work.
The core difference
Quality is about kind and standard. Quantity is about amount. The two are independent: something can be plentiful and awful, or scarce and superb, which is precisely why the phrase quality over quantity exists.
Quality carries a second, older sense too — a characteristic or attribute, with no judgement attached: Patience is a quality I lack. Quantity has no equivalent second meaning.
How to use each
- The sound quality on the recording is poor. (standard)
- Her best quality is that she asks before assuming. (characteristic)
- Quality of life matters more than square footage.
- They shipped the wrong quantity — 200 units, not 20.
- Large quantities of rainwater collect on the flat roof.
A test you can run
Ask which question your sentence answers:
- "How good is it?" or "What is it like?" → quality.
- "How much?" or "How many?" → quantity.
You can also test with a number. If a figure could replace the word's meaning — 200 units, 40 litres, half a tonne — you are talking about quantity.
The memory trick
Quantity begins like quantify, which is what you do with numbers. Quality shares its opening with qualify and qualities — describing what something is like, not counting it.
Grammar worth knowing
Quality works as a modifier in front of a noun, meaning "good": quality ingredients, a quality finish. This is standard in commercial English, though some careful writers avoid it as marketing-speak — high-quality ingredients is the safer choice in formal prose, because quality on its own is strictly neutral and needs an adjective to say whether the standard is high or low.
Quantity never works that way. "A quantity report" is odd; write a report on quantities or use volume.
Both are countable or uncountable depending on sense: the quality of the light (uncountable) versus her many qualities (countable); a small quantity of salt versus large quantities of data.
The common mistake
The frequent slip is writing quality where a bare amount is meant — "the quality of applicants doubled" when what doubled was the number. If a figure went up or down, the word is quantity, or better still number for countable things and amount for uncountable ones. Quantity itself often sounds bureaucratic in ordinary prose: a lot of water reads better than a large quantity of water outside a technical document.
Frequently Asked Questions
What does "quality over quantity" mean?
It means a few good things beat many mediocre ones — one thoughtful application beats twenty generic ones. The phrase only makes sense because the two measures are independent of each other.
Is "quality" always positive?
Not strictly. In its precise sense it is neutral — you can have <em>poor quality</em>. Used before a noun (<em>quality service</em>) it does mean good, but formal writing usually prefers <em>high-quality</em> to make that explicit.
Should I use quantity, number or amount?
Use <em>number</em> for things you count (<em>the number of complaints</em>), <em>amount</em> for things you measure (<em>the amount of water</em>), and reserve <em>quantity</em> for technical or commercial contexts where a measured total is meant.