Step 1: Wide acceptability: A national language must be spoken and understood by a large majority of the population across regions, serving as a common medium of communication that transcends local/regional languages.
Step 2: Cultural and historical roots: It should carry deep historical and cultural roots within the nation, reflecting its literature, traditions, and collective identity, giving citizens a sense of shared heritage.
Step 3: Administrative and educational capacity: It should be capable of serving as a medium for administration, law, education, and scientific/technical expression, with a rich enough vocabulary and literary tradition to support these functions.
Step 4: Unifying and integrative role: It should function as a unifying link between diverse linguistic and cultural groups, fostering national integration without erasing the identity of other regional languages.
Final Answer: A national language is characterized by wide acceptability, deep cultural roots, administrative/educational capacity, and a unifying, integrative role across the nation.