Turkestan vs Turkistan

Turkestan and Turkistan both are nouns.

Word	Noun	Adjective	Verb	Adverb
Turkestan	Yes	No	No	No
Turkistan	Yes	No	No	No

As nouns, Turkestan and Turkistan are synonyms defined as:

Turkestan and Turkistan: a historical region of central Asia that was a center for trade between the East and the West

Turkestan (noun)	Turkistan (noun)
a historical region of central Asia that was a center for trade between the East and the West	a historical region of central Asia that was a center for trade between the East and the West