This page explains the terms strong and weak as applied to acids. As a part of this it defines and explains what is meant by pH, Ka and pKa.
Strong acids
Explaining the term "strong acid"
We are going to use the Bronsted-Lowry definition of an acid.
When an acid dissolves in water, a proton (hydrogen ion) is transferred to a water molecule to produce a hydroxonium ion and a negative ion depending on what acid you are starting from.
In the general case . . .