acid
A-sihd
Acid (noun) means In chemistry, a substance that reacts with a base, tastes sour, and can turn litmus paper red; on the pH scale it measures below 7. Example: “Vinegar contains a mild acid called acetic acid.”
noun
1
In chemistry, a substance that reacts with a base, tastes sour, and can turn litmus paper red; on the pH scale it measures below 7.
"Vinegar contains a mild acid called acetic acid."
"The chemist wore gloves while handling the strong acid."
"Lemon juice contains citric acid, which gives it its sharp taste."
2
Slang for LSD, a powerful hallucinogenic drug.
"He claimed the band wrote the album after dropping acid."
"The film shows a character who takes acid and sees swirling colours everywhere."
"Some psychedelic art was inspired by people who took acid."
adjective
1
Sour or sharp-tasting, like vinegar.
"The wine had an acid tang that made her wince."
"These green apples are too acid for me without any sugar."
"The sauce turned acid after sitting in the sun all afternoon."
How to use acid
Learner’s notesIn plain EnglishA sour or corrosive chemical substance — or, informally, the drug LSD.
When to use it
The drug sense is informal slang, not used in medical or scientific writing.
Common pairings
stomach acid
acid rain
acid test
drop acid
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Word forms
- Plural
- acids
- Comparative
- acider
- Superlative
- acidest
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Can you complete this real example?
Vinegar contains a mild _____ called acetic acid.
Etymology
From French acide, from Latin acidus, "sour," related to the verb aceo, "to be sour."
Synonyms
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Related words
Rhymes for acid
See all rhymes for acid →Frequently asked questions
What does “acid” mean?
The word “acid” means in chemistry, a substance that reacts with a base, tastes sour, and can turn litmus paper red; on the pH scale it measures below 7. In plain terms, a sour or corrosive chemical substance — or, informally, the drug LSD.
How do you pronounce “acid”?
“Acid” is pronounced A-sihd (/ˈæsɪd/ in IPA).
How do you use “acid” in a sentence?
Here is “acid” used in a sentence: “Vinegar contains a mild acid called acetic acid.”
What is another word for “acid”?
Words with a similar meaning to “acid” include acidic.
What is the opposite of “acid”?
The opposite of “acid” — its antonyms — are alkaline, base and alkali.
What part of speech is “acid”?
Depending on how it is used, “acid” can be a noun and an adjective.
Where does the word “acid” come from?
The word “acid” comes from Latin. From French acide, from Latin acidus, "sour," related to the verb aceo, "to be sour.".
Is “acid” a common word?
“Acid” is a fairly common word in modern English, usually learned at around the B2 level.
What is the difference between an acid and a base?
Acids and bases are chemical opposites. An acid tastes sour, turns litmus paper red, and measures below 7 on the pH scale. A base, or alkali, tastes bitter, feels slippery, turns litmus blue, and measures above 7. When mixed, an acid and a base react and neutralise each other, forming a salt and water.
What are some examples of acids?
Everyday acids include the citric acid in lemons and oranges, acetic acid in vinegar, and lactic acid in sour milk. Your stomach uses hydrochloric acid to digest food. Industrial and laboratory acids include sulfuric, hydrochloric, and nitric acid, which are far stronger and highly corrosive. Acids range widely in strength.
How can you tell if a substance is an acid?
The classic test is litmus paper, which an acid turns red. A pH reading below 7 also confirms it, with lower numbers meaning stronger acidity. A sour taste is another traditional sign, think lemon or vinegar, though tasting unknown chemicals is never safe. Indicators and pH meters are the reliable methods.
Are all acids dangerous?
No. Strength matters. Strong acids like sulfuric or hydrochloric are corrosive and can burn skin, so they demand care. But weak acids are all around us and harmless in normal amounts, since the citric acid in fruit and the acetic acid in vinegar are safe to eat. Concentration and type decide the risk.
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