▁du i ▁da ▁( <0xE5> <0xB0> <0x8D> 打 ) ▁or ▁du i ▁li an ▁( <0xE5> <0xB0> <0x8D> <0xE7> <0xB7> <0xB4> ), ▁were ▁an ▁essential ▁part ▁of ▁Chinese ▁mart ial ▁arts ▁for ▁centuries . ▁D ui ▁li an ▁means , ▁to ▁train ▁by ▁a ▁pair ▁of ▁combat ants ▁oppos ing ▁each ▁other — the ▁character ▁li an ▁( <0xE7> <0xB7> <0xB4> ), ▁refer es ▁to ▁practice ; ▁to ▁train ; ▁to ▁perfect ▁one ' s ▁skill ; ▁to ▁dr ill . ▁As ▁well , ▁often ▁one ▁of ▁these ▁terms ▁are ▁also ▁included ▁in ▁the ▁name ▁of ▁fighting ▁sets ▁( <0xE9> <0x9B> <0x99> <0xE6> <0xBC> <0x94> ; ▁sh u ang ▁y an ), ▁" pa ired ▁practice " ▁( <0xE6> <0x8E> <0x99> 勝 ; ▁z h eng ▁sh eng ), ▁" to ▁struggle ▁with ▁strength ▁for ▁victory " ▁( <0xE6> <0x95> <0xB5> ; ▁di ), ▁match ▁– ▁the ▁character ▁suggests ▁to ▁strike ▁an ▁enemy ; ▁and ▁" to ▁break " ▁( <0xE7> <0xA0> <0xB4> ; ▁po ). ▁ ▁Gener ally , ▁there ▁are ▁ 2 1 , ▁ 1 8 , ▁ 1 2 , ▁ 9 ▁or ▁ 5 ▁dr ills ▁or ▁' ex changes / group ings ' ▁of ▁attacks ▁and ▁counter att acks , ▁in ▁each ▁du i ▁li an ▁set . ▁These ▁dr ills ▁were ▁considered ▁only ▁generic ▁patterns ▁and ▁never ▁meant ▁to ▁be ▁considered ▁inf lex ible ▁' tr icks '. ▁Stud ents ▁pract iced ▁smaller ▁parts / ex changes , ▁individually ▁with ▁oppon ents ▁switching ▁sides ▁in ▁a