The state, quality, or degree of being acid.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "acidity" in a sentence
"Taste again when the acidity is at a level you like."
"No doubt it’s true that the oceans increase in acidity is all made up, too."
"Lemon's acidity is what some people like but not me."