To make something natural or to adapt to nature.

To grant citizenship to a foreign-born person.

विदेशी नागरिक को नागरिकता देना।

English Usage: After several years of residency, he was finally able to naturalise as a citizen.

Hindi Usage: कई वर्षों तक निवास करने के बाद, वह अंततः नागरिक के रूप में प्राकृतिक बन सका।