zi 咨, communications between institutions of the same level

The expressions zi 咨, zihui 咨會, ziwen 咨文 or zixing 咨行 were used to denote communications between institutions of the same level (pingxing wen 平行文) and belonging to different jurisdictions. It was originally used during the Tang 唐 (618-907) and Song 宋 (960-1279) periods for communication from the Hanlin Academy 翰林院 to the Counsellor-in-chief (zaixiang 宰相) or the Palace Secretariat (zhongshusheng 中書省). In this meaning, it was also called zibao 咨報 or 諮報. For all other "lateral communication", the term zhuang 狀 was used.

From the Yuan period 元 (1279-1368) on, the short term zi became the standard designation for this type of document. The Ming 明 (1368-1644) and Qing 清 (1644-1911) dynasties continued this form of document for communication on the highest levels of central and provincial administration: During the Ming period, the type of document was used among the Six Ministries (liubu 六部) or between the Ministries and the regional military commissions (du zhihuishi si 都指揮使司). In the Qing period, it was used between Ministries and institutions on the same level (buyuan 部院) and governor-generals (zongdu 總督), provincial governors (xunfu 巡撫), Banner commanders-in-chief (dutong 都統) and provincial Banner generals (jiangjun 將軍), between governor-generals and governors or between provincial commissioners (si 司, i.e. buzhengshi 布政使 and anchashi 按察使) and circuit intendants (dao 道). When crossing the border of the civilian and military realms, governor-generals and provincial governors used zi-type communications to address provincial military commanders (tidu 提督, see Green Standard Army), provincial governors, provincial commissioners or circuit intendants to address regional commanders (zongbing 總兵), or the two provincial commissioners addressing assistant regional commanders (canjiang 參將) or brigade commanders (youji 游擊).

Zi-type documents were used for discussion, request and reports. In the early Qing period, the leporello-style (zheshi 折式) and the card-style (zhuangshi 狀式) form were both used. The document was sealed by the sender, and bore the word zi 咨 on the cover page. The typical beginning of zi-type documents was "X writes concerning Y" (mou bu wei mou shi yunyun 某部為某事云云), while the closing formula was "we ask to execute the instruction of this communication after careful examination, on behalf of the sender" (hexing yizi, qing zhao yan shixing, xu zhi zizhe 合行移咨，請照驗施行，須至咨者).

Documents delivered to an institution of somewhat higher standing were called zicheng 咨呈 (see chengwen 呈文). During the Yuan period, it was used by province heads (xingsheng 行省) when addressing central-government departments (dusheng 都省, i.e. shangshusheng 尚書省 or zhongshusheng). When the latter wrote to provincial heads, the document was called zifu 咨付.

The Ming dynasty used zicheng documents when the metropolitan prefecture Yingtian 應天府 (i.e. Nanjing) wrote to a regional military commission 都司 or a provincial administration commission (布政司), when one of the Six Ministries wrote to one of the Five Chief Military Commissions (wujun dudufu 五軍督都府), when a prefect wrote to the provincial surveillance commission (anchasi 按察司) or the latter to the provincial administration commission, or the latter to a Ministry. Yet documents dispatched into the opposite direction, e.g. one of the Five Chief Military Commissions to a Ministry, the document was called "notification" (zhaohui 照會).

During the Qing period, zicheng-type communications were dispatched by Ministries to the Court of the Imperial Clan (zongrenfu 宗人府), the metropolitan prefecture Shuntian 順天府 (i.e. the government of Beijing) to one of the Six Ministries or to the Censorate (duchayuan 都察院), the various courts (si 寺) and directorates (jian 監) or central bureaus (ju 局) writing to one of the Six Ministries, provincial Banner generals (jiangjun) and governor-generals and governors (du-fu 督撫) writing to the State Council (junjichu 軍機處), provincial commissioners and circuit intendants (si-dao 司道) writing to provincial military commanders (tidu) or to one of the Ministries, or prefects and district magistrates writing to regional commanders (zongbing).

The word zi can also be used adverbially, e.g. zi wen 咨問 "asking by a letter of lateral communication".