Question

define bascity of an acid and acidity of a base

Answer 1

Hey mate!!
Here's your answer :)

Basicity of an acid is defined as the number of replaceable H+ ions
AND
Acidity of a base is the number of replaceable OH- ions.
For example basicity of HCl is 1; HCl in aq gives H+ and Cl- AND acidity of NaOH is 1; NaOH in aq gives Na+ and OH- !!

Hope this helps☺☺

Answer 2

The basicity of an acid is the number of hydrogen ions, which can be produced by one molecule of the acid. 
Acidity of base is defined as the no of ionizable hydrogen ions (OH-) present in one molecule of a base.

NaOH(aq)Na+ + OH- : Acidity = 1
Ca(OH)2(aq) Ca+2 + 2OH- : Acidity = 2

BASE