Hydrochloric acid (HCl) is described as a strong acid because, in water, it:

1. The strength of an acid is defined by how completely it releases its hydrogen ions in solution, not by how corrosive it "feels." 2. The text states: "hydrochloric acid (HCl) completely dissociates into" its ions in water. 3. A weak acid, by contrast, only partially ionizes -- most of its molecules remain intact in solution. 4. So HCl is called a strong acid specifically because it fully dissociates in water, rather than only partially ionizing. _Source: OpenStax Biology Ch 2 "The Chemical Foundation of Life", p.51 §2.2 | Water_