Chinese punctuation has punctuation marks that are derived from both Chinese and Western sources. Although there was a long native tradition of textual annotation to indicate the boundaries of sentences and clauses, the concept of punctuation marks being a mandatory and integral part of the text was only adapted in the written language during the 20th century due to Western influence. Before that, the concept of punctuation in Chinese literature existed mainly in the form of judou (traditional Chinese: 句讀; simplified Chinese: 句读; pinyin: jù dòu; lit. 'sentences and clauses'), a system of annotations denoting stops and pauses. However, unlike modern punctuation, judou marks were added into a text by scholars to aid comprehension, and for pedagogical purposes and were not viewed as an integr