Select the INCORRECTLY spelt word.

Correct option is D

Option (d) is the incorrectly spelt word.
Correct spelling is: "Millennium" – It means a period of a thousand years. (एक सहस्त्राब्दी / हज़ार वर्ष)
Part of Speech: Noun
Example: The year 2000 was celebrated as the beginning of a millennium.
Meanings of all the given options:
· (a) Inoculate: To inject a vaccine (टीका लगाना)
· (b) Leisure: Free time (अवकाश)
· (c) Medieval: Related to the Middle Ages (मध्ययुगीन)