Ivan Turgenev vs Ivan Sergeevich Turgenev

Ivan Turgenev and Ivan Sergeevich Turgenev both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ivan Turgenev	Yes	No	No	No
Ivan Sergeevich Turgenev	Yes	No	No	No

As nouns, Ivan Turgenev and Ivan Sergeevich Turgenev are synonyms defined as:

Ivan Turgenev and Ivan Sergeevich Turgenev: Russian writer of stories and novels and plays (1818-1883)

Other synonyms of Ivan Turgenev include Turgenev.

Ivan Turgenev (noun)	Ivan Sergeevich Turgenev (noun)
Russian writer of stories and novels and plays (1818-1883)	Russian writer of stories and novels and plays (1818-1883)