The word 沉溺 (chénnì) is formed through the combination of two semantically similar characters, creating a compound word with an intensified meaning. The first character, 沉 (chén), means "to sink" or "to submerge," while the second, 溺 (nì), means "to drown." Together, they form a vivid metaphor of being completely immersed and overwhelmed, as if sinking and drowning in water, which figuratively translates to being deeply engrossed, addicted, or indulging excessively in an activity or state (often with a negative connotation). This structure exemplifies a common Chinese lexical pattern where two near-synonyms are paired to express a more specific and potent concept.