of chief importance; principal

happening first in time or order

प्राथमिक

English Usage: He was the primary author of the report.

Hindi Usage: वह रिपोर्ट का प्राथमिक लेखक था।

a publication issued at regular intervals

occurring at intervals

अवधिक

English Usage: He made periodical visits to the clinic.

Hindi Usage: उसने क्लिनिक में अवधिक दौरे किए।