Is a Cosmo a martini?

Could you please clarify for me? Is a Cosmo truly considered a martini, or does it merely share some similarities? I've always been curious about the drink's classification. Is the Cosmopolitan merely a variant of the classic martini, or does it belong to a different category of cocktails? Its ingredients and preparation methods seem to have some overlap, but I'm not entirely sure if that's enough to categorize it as a martini. Could you enlighten me on this matter?