In naphthalene an amino group occupies an alpha position (C-1) and a methyl group is on the adjacent beta carbon (C-2). Which is the correct name?

Amine is the principal characteristic group, expressed as the suffix 'amine' and given the lowest locant (1). The methyl is a prefix at C-2. The name is 2-methylnaphthalen-1-amine; swapping the locants describes a different compound, and the prefix-only name ignores the principal group suffix.