This is an Arabic word that is used in many ways .
The Qadiani Ahmadiyya have taken this word to mean the occupier of the 'Khilafat' - the seat of the Caliphate, and termed it 'Khalifatul Masih' - the successor to the Messiah
According to purists, although this term could have applied to Hakeem Nooruddin, who was the successor to Mirza Ghulam Ahmad, anybody else would have to be a successor to the former. Similarly, the non-Arabic understanding of the Arabic word 'Khilafah' is more of a continuing dynasty.