acid

acid — noun

1. a chemical that tastes sharp, has a low pH, and in strong forms can eat into met

1.nounB2
Definition

a chemical that tastes sharp, has a low pH, and in strong forms can eat into metal, skin, or fabric.

Example

Lemon juice contains a mild acid that gives the fruit its sharp taste.

subject is a real-world food/liquid containing acid

A drop of strong acid burned a small hole through Ben's cotton shirt.

collocation: strong acid + burn through

Common collocations
  • strong acid
  • mild acid
  • stomach acid
  • battery acid
  • pour acid on something
Antonyms
  • base

    the chemical opposite of an acid; bases have a high pH

  • alkali

    another word for a base, especially one that dissolves in water

Usage Note

Common in both countable and uncountable use: 'an acid' for one specific kind, 'acid' as a substance in general. Often paired with strength words like 'strong', 'mild', 'weak', 'concentrated'.

Common Mistakes

The acid is taste sour.
The acid tastes sour.
'taste' is the verb here; do not insert 'is'.
She poured an acid on the metal.
She poured acid on the metal.
use uncountable when you mean acid in general.

2. a slang word for the powerful illegal drug LSD, which makes the user imagine sig

2.noun
Definition

a slang word for the powerful illegal drug LSD, which makes the user imagine sights and sounds that aren't real.

Example

Police arrested two students for selling acid at a music festival in Brighton.

informal noun for LSD; uncountable

Eitan said he had tried acid only once during his college years.

collocation: try acid

Common collocations
  • take acid
  • drop acid
  • be on acid
  • sell acid
Synonyms
  • LSD

    the formal scientific name for the same drug

Usage Note

Always uncountable in this sense and limited to informal speech and writing. Not used with 'an' or in plural form. Distinguish from sense 1, which is countable and refers to chemical substances.

Common Mistakes

He bought two acids at the party.
He bought some acid at the party.
this drug sense is uncountable.

acid — adjective

Word family

  • acidic
    adjectiveC1
  • acidity
    nounC1
  • acidify
    verbC2
  • acidly
    adverbC2

Synonym discussion

Sense: adjective/1

These four words all describe a sharp taste, but learners use them in different settings. 'Sour' is the everyday choice — anyone might call lemon juice or unripe fruit sour at the dinner table. 'Tart' often carries a positive note: a tart cherry pie sounds appealing rather than unpleasant. 'Acidic' is the most useful general adjective: it works for taste ('an acidic wine') and for chemistry ('acidic soil', 'acidic water'). 'Acid' as an adjective is a little older and now mostly survives in fixed pairs like 'acid rain', 'acid soil', and 'acid drop' (a candy); for free use, 'acidic' sounds more natural. So: say 'sour' at meals, 'tart' for baking and cooking notes, 'acidic' in science class, and keep 'acid' for the set phrases.

acid ↗acidic ↗sour ↗tart

Common collocations

Nouns

Adverbs

Phrases

  • acid rain
  • acid test
  • acid trip
  • drop acid
  • the acid test of something

Prepositions

  • of (full of acid)
  • in (rich in acid)

Etymology

LatinFrenchEnglish

The word 'acid' came into English in the early 1600s from the Latin word 'acidus', meaning 'sour' or 'sharp', which itself grew from the verb 'acere', 'to be sour'. It first entered English as an adjective for things that taste sharp, then within a few decades chemists began using it as a noun for sour-tasting substances. The slang use for the drug LSD appeared in the 1960s in American English, picking up on the chemical compound's full name, 'lysergic acid diethylamide'. The figurative meaning 'sharp and unkind in tone' was already in use by the 1800s, building naturally on the taste sense.