Complex sentence: Western Armenia, formerly referred to as Turkish Armenia (see below), is a term, primarily used by the Armenians, to the areas of the Ottoman Empire with significant number of Armenians that were exterminated during the Armenian Genocide in 1915 and the following years.
Split into simpler sentences: Western Armenia, formerly referred to as Turkish Armenia (see below), is a term, primarily used by the Armenians, to refer to formerly Armenian-inhabited areas of the Ottoman Empire. Its native Armenian population was exterminated during the Armenian Genocide in 1915 and the following years.