What type of suffix is “-able” considered?

The suffix "-able" is considered an adjective suffix because it is used to form adjectives indicating that something is capable of or suitable for a certain action or quality. For example, in the word "readable," the suffix "-able" implies that something can be read. This indicates a characteristic of the noun it modifies, thereby categorizing it as an adjective.

In contrast, noun suffixes typically denote the name of a person, place, thing, or idea and do not convey the capability or suitability inherent in the use of "-able." Verb suffixes usually indicate an action or state and are not focused on describing qualities. Adverb suffixes modify verbs, adjectives, or other adverbs, and, while "-able" can relate to actions, its key function lies in its ability to describe adjectives rather than adverbial function. This makes "-able" distinctly an adjective suffix.