A weak acid is an acid that partially dissociates in water, leading to a pH less than 7. However, there are several synonyms or related terms used in chemistry for weak acids, including mild acidity, moderately acidic, partially ionized, and less vigorous acidic. The term "mild acidity" refers to weak acids that have a relatively low ionization constant and a pH close to 7 in water. "Moderately acidic" implies that the acid is weaker than strong acids but still acidic in nature. The term "partially ionized" describes the phenomenon where a weak acid dissociates only partially in water, whereas "less vigorous acidic" refers to a weak acid that does not exhibit the characteristic properties of a strong acid.