统 is a bound morpheme (b.f.) — it never stands alone as a word. It appears as the first or second element in many compound words, carrying the core ideas of 'uniting', 'system', or 'overall'. Common compounds include 统一 (tǒngyī, to unify/unified), 系统 (xìtǒng, system), 统计 (tǒngjì, statistics), and 传统 (chuántǒng, tradition). Understanding this morpheme helps decipher dozens of HSK 5-7 vocabulary items.