How many Rak'ahs of Tarawih prayer can a sick person pray at home, and is that sufficient in place of Qiyam al-Layl?

Qiyam (definition) al-Layl (Night Vigil) in Ramadan (definition) and other months is a confirmed Sunnah (definition) (Prophetic tradition). Its importance is even more emphasized in Ramadan due to the Hadith (definition): "Whoever stands in prayer during Ramadan with faith and expecting Allah's reward will have his past sins forgiven." The performance of Qiyam Ramadan is achieved by praying Taraweeh, either at home or in the mosque, in congregation or individually, at any time between 'Isha (night) prayer and Fajr (dawn) prayer. The most complete way is to pray eleven rak'ahs, following the example of the Prophet (peace be upon him), and there is no harm in increasing or decreasing the number of rak'ahs.