Tehran vs Teheran

Tehran and Teheran both are nouns.

Word	Noun	Adjective	Verb	Adverb
Tehran	Yes	No	No	No
Teheran	Yes	No	No	No

As nouns, Tehran and Teheran are synonyms defined as:

Tehran and Teheran: the capital and largest city of Iran; located in northern Iran

Other synonyms of Tehran include capital of Iran, Iranian capital.

Tehran (noun)	Teheran (noun)
the capital and largest city of Iran; located in northern Iran	the capital and largest city of Iran; located in northern Iran