Each Surah of the Holy Quran is divided into several sections known as Rukus. A Ruku consists of a number of
aayats all of which deal with one topic. There are 540 Rukus in The Holy Quran.
The Rukus of The Holy Quran were not to be found in the time of Nabi Muhammad sallallahu alaihi wasallam, nor in the time of the Sahaaba radhiyallahu anhum.
Around the 4th century of the Hijri calendar the Ulema of Bukhara, Russia divided the entire Quran into 540 Rukus for Taraaweeh purposes.
They reckoned that if one Ruku is recited in each raka’at of the Taraaweeh salaah the Hafiz will finish the Quran exactly on the 27th night of Ramadaan. The equation is as follows:
1 ruku per raka’at x 20 raka’ats = 20 Rukus per night x 27 nights = 540 rukus.
When devising these Rukus the Ulema made sure that Rukus contained aayats of the same topic and theme.
They named it Ruku because the Hafiz goes into ruku after reciting it in one raka’at of Taraaweeh salaah.
NOTE: It is not wajib or necessary to make ruku after reading a ruku in Taraaweeh or any other salaah. One can make ruku at the end of any aayat. These Rukus were formulated simply to ease matters for the hafiz during Taraaweeh.