General English


  • noun a chemical compound containing hydrogen which dissolves in water and forms hydrogen ions, or reacts with an alkali to form a salt and water, and turns litmus paper red


  • noun a chemical substance which reacts with a base to form a salt


  • A liquid that has a pH of less than 7.0.


  • A chemical which has any of the following characteristics: increases the proportion of hydrogen ions in a solution, gives up a proton in solution, has at least one hydrogen that can be replaced by metals or basic radicals, that can react with a base to form a salt, or that accepts two electrons. According to the pH scale, an acid has a reading of less than 7.0, while a base (6) has a value above 7.0. The lower the reading, the stronger the acid.


  • A substance containing an excess of hydrogen ions when compared with pure water, which contains equal amounts of hydrogen ions (acid forming) and hydroxyl ions (alkali forming). This excess causes the characteristic sour taste response.


  • noun LSD-25, the synthetic hallucinogenic drug. From the full name, Lysergic Acid Diethylamide. This has been the standard term by which users refer to the drug since its first popularity in California in 1965, in spite of the appearance of more picturesque but ephemeral alternatives. In the late 1980s, adherents of the acid house cult adopted the word as a slogan (usually a cry of ‘a-c-e-e-e-d!’) and to refer to LSD or ecstasy.
  • noun sarcasm, snide comments or cheeky exaggeration, especially in the expression ‘come the old acid’, popular in working-class usage in the 1950s and 1960s and still heard. In such phrases as ‘his acid comments’ the adjectival meaning is similar, but cannot be described as slang.


  • a chemical that is present in grapes and is produced during the fermentation process. Grapes from cooler regions or seasons have higher acid levels, while grapes from warmer climates have lower acid levels. In wine the acids provide the sharpness and definition to the taste of the wine. The three main acids that occur naturally in a wine are tartaric, malic, and citric acids. Each has a different function: tartaric acid provides the sharpness of a wine and ensures that the ageing process enhances the complexity of the wine, while malic acid is often responsible for the fruity smell and taste of a wine. The most dominant acid in a wine is tartaric, but the levels of all acids are measured (in a process called titration) to produce the total acid content, written as a percentage of total acids per litre of wine. Dry wines have a total acid content of around 0.7 per cent, while sweet wines have one around 0.8 per cent. In a well-balanced wine, the acid content should enhance the taste and should not be a noticeable element – during assemblage, the winemaker can alter the acid levels by blending wines from different batches of grapes or grapes picked at different times. Those left on the vine longer have higher levels of sugar and lower acid levels.
  • used to describe a wine that tastes very sharp or sour due to an excess of acid

Origin & History of “acid”

The original notion contained in the word acid is ‘pointedness’. In common with a wide range of other English words (e.g. acute, acne, edge, oxygen) it can be traced back ultimately to the Indo-European base *ak-, which meant ‘be pointed or sharp’. among the Latin derivatives of this base was the adjective ācer ‘sharp’. From this was formed the verb acere ‘be sharp or sour’, and from this verb in turn the adjective acidus ‘sour’. The scientist Francis bacon seems to have been the first to introduce it into English, in the early 17th century (though whether directly from Latin or from French acide is not clear). Its use as a noun, in the strict technical sense of a class of substances that react with alkalis or bases, developed during the 18th century.