The word 难以 is formed through the combination of the independent character 难 (nán), meaning "difficult", with the classical grammatical particle 以 (yǐ), which here functions as a connective binder. This fusion creates a single, unified adverb where 以 loses its standalone lexical meaning and instead serves to extend and modify the core concept of "difficulty", allowing it to seamlessly preface a verb that follows. The formation is thus a lexicalization, a freezing of a once-flexible grammatical structure into a fixed, compound word expressing the notion of "hard to" or "difficult to" accomplish something.