felix

Felix, felicis is a third declension adjective of one termination: a single nominative singular for all three genders, with everything else built on the stem felic-. It declines as an i-stem, so ablative singular felici, genitive plural felicium, neuter plural felicia.

The root sense is fertile, of soil and of trees, and the luck sense grows out of it: what bears fruit is blessed. Sulla took Felix as a formal cognomen, staking a public claim on divine favour. The dark twin is the arbor infelix, the barren tree, which was also the technical name for the gallows. Comparative felicior, superlative felicissimus, adverb feliciter, which is the standard Latin for "good luck" scratched on a wall.