/ ˈsəʊdə; NAmE ˈsoʊdə/ noun
1.
[ U , C ] = soda water :
a Scotch and soda
2.
(also old-fashioned ˈsoda pop ) (both NAmE ) [ U , C ] a sweet fizzy drink (= a drink with bubbles) made with soda water, fruit flavour and sometimes ice cream :
He had an ice-cream soda.
3.
[ U ] a chemical substance in common use that is a compound of sodium :
baking / washing soda
—see also caustic soda , sodium bicarbonate , sodium carbonate
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WORD ORIGIN
late Middle English (in sense 3): from medieval Latin , from Arabic suwwad saltwort (a plant whose ashes were formally used in soap making).