Definition of a "Feeble" acid? I'm currently trying to re-familiarize myself with chemistry, after a very long absence of any study in this field. At the moment I'm working my way through the text "Fundamentals of Chemistry" by "David E Goldberg" and I notice the author introduces the concept of "feeble" acids (and bases). I was familiar with the concept of weak (partially dissociated) acids versus strong (near 100% dissociated) acids. However the distinction between a weak acid and a feeble acid is not something I've come across before. It's clear from the text that a "feeble" acid is weaker than a "weak" acid, but the author doesn't make it all that clear where exactly "weak" ends and "feeble" begins. Googling for the term "feeble acid" doesn't seem to reveal many relevant hits, so I'm not even sure how widely this distinction between weak/feeble is actually used. Just wondering if anyone can shed a bit more light on this for me. Is there a particular value of dissociation constant (say 10^-8 for example) below which one can say that an acid is feeble?