Definition of Director Identification Number clarifies identity rules and incorporates prior identifiers for corporate compliance. These Rules define operative terms for the Companies Act, designating Director Identification Number (DIN) including prior DINs and DPIN, and specifying digital compliance mechanisms such as Digital Signature Certificate, electronic record, electronic registry, electronic mode (covering B2B/B2C, deposits, online services and data communications), Certifying Authority, e-Form, Registrar's Front Office and Pre-fill. They treat a holding company director or key managerial personnel and their relatives as related parties and list specific relatives for related-party and disqualification purposes.