Ruku

Rukūʿ (Arabic: رُكوع‎‎) refers to a paragraph of the holy book Qur'an. There 558 or at some books 540 Ruku in Holy Quran. In prayer it refers to the bowing down from the standing position while praying according to Islamic ritual (salat). There is a consensus on the obligatory nature of the rukūʿ. The position of rukūʿ is established by bending over, putting one's hands on one's knees, and remaining in that position until the individual attains "calmness".

In Al-Ghazali's book Inner Dimensions of Islamic Worship, he wrote about the rukūʿ by saying:

The term rukūʿ — roughly translated to "passage", "pericope" or "stanza" — is also used to denote a group of thematically related verses in the Qur'an. Longer suras (chapters) in the Qur'an are usually divided into several rukūʿs, so that the reciters could identify when to make rukūʿ in Salat without breaking an ongoing topic in the Quranic text.

...
Wikipedia