The word 单词 is formed by directly combining two meaningful characters: 单 (dān), which conveys the idea of "single", "solitary", or "one", with 词 (cí), which means "word" or "term". The formation is conceptually straightforward, where the first character descriptively modifies the second; it literally means a "single word", highlighting an individual, standalone lexical unit as opposed to a phrase or sentence. This structure creates a compound whose meaning is essentially the sum of its transparent parts, defining a specific and common concept in language.