Other forms: acids
An acid is a sour substance that turns litmus red and eats metal. A strong acid, acid rain, stomach acid.
On the pH scale anything below seven is acid, and each step is a tenfold change — so a pH of three is a hundred times more acid than a pH of five. Stomach acid is strong enough to dissolve metal. Figuratively an acid remark is sharply sour. Note that the Latin means sour.
1nounacidA sour substance that turns litmus red.
“Wear goggles in the lab, because the acid can burn your eyes.”
2adjectivesharplySharply sour in taste or manner.
“She made an acid comment about his cooking that silenced the whole table.”
Too few real examples of this word to estimate which sense is commonest.
acid is a substance.
Latin acidus means sour, from acere, to be sour. Acute, acrid and vinegar's acetic come from the same sharpness.
Proto-Indo-European
*h₂eḱ-
French
acide
English, today
acid
Built from
Borrowed from French acide. From French acide, from Latin acidus (“sour, acid”), from aceō (“to be sour”). a doublet of agita.
Etymology from Wiktionary, CC BY-SA