In the absence of a definition, I'll provide one. What is a 13 letter word for vertical? Answer: perpendicular
Correspondent
acceptabilityaccommodationadvertisementalternatively
degenerationsdeterioratingdisintegratesinterregionalinterrelatinginterrelationintransigentsnonintegratednonregisteredregenerationsregistrationsreintegration
Hydromagnetic.
disagreement
Excommunicate is a 13 letter word. It begins and ends with the letter e.
Boardinghouse and brainstorming are 13 letter words. The 3rd letter is the letter a.
Some 13 letter words that start with the letter a:abbreviationsabnormalitiesacceptabilityaccessibilityaccommodationaccreditationacquaintancesacupuncturistadministratoradmissibilityadvertisementaffordabilityalgebraicallyalternativelyanniversariesannouncementsanticipationsapplicabilityappropriationapproximationarchitecturalassassinationassignabilityastonishinglyattainabilityattentivenessauthenticallyauthoritativeauthorization
Correspondent
perpendicular
A 13-letter word that starts with "s" and ends with "s" is "schoolteachers."
encouragement
quadrilateral
acceptabilityaccommodationadvertisementalternatively
unimaginative
degenerationsdeterioratingdisintegratesinterregionalinterrelatinginterrelationintransigentsnonintegratednonregisteredregenerationsregistrationsreintegration
international