planetas

Planetas is masculine in Spanish because it derives from Latin "planēta," which borrowed the Greek word "planḗtēs" (πλανήτης, meaning "wanderer"). Although Greek nouns ending in -ēs were typically masculine, Latin "planēta" ends in -a and follows the Latin first declension pattern, which would normally indicate feminine gender. However, "planeta" is treated as masculine in Spanish due to its Greek origin and the semantic association with the masculine noun "astro" (heavenly body), which influenced gender assignment in Romance languages.