Persius on vanity

Something trivial getting under your skin? Persius knows this! O curas hominum! O quantum est in rebus inane! Oh, the cares of humans! Oh, how much is vain in their affairs! O is an exclamation or interjection. Curas (cares or anxiety) is an a declension feminine noun in the accusative plural form of "cura." Hominum (of humans or of men) is an i stem masculine noun in the genitive plural form of "homo." Quantum (how much) is an a/o declension neuter adjective in the nominative singular form. Est (is) In (in or within) Rebus (affairs or concerns) is an e declension feminine noun in the ablative plural form of "res." Here used to specify where the inane exists. Inane (empty or vain) is a mixed declension neuter adjective in the nominative singular form, agreeing with quantum. It functions as a predicate adjective, providing more information about the subject, which is "quantum" in this context.