The word "纤细" is formed by combining the character "纤", which consists of the silk radical (纟) indicating relation to threads and the phonetic component "千" suggesting pronunciation and contributing to its meaning of fineness, with the character "细", which also contains the silk radical (纟) for thematic consistency and the phonetic component "囟" for sound, conveying thinness. Together, these characters create a compound word where the shared radical reinforces the concept of slenderness or delicacy, directly derived from the attributes of fine threads.