This is the 15023rd most frequent German word.
sechsten
"Sechsten" means "sixth" (in the dative case) in English.
sechsten is used here as an ordinal number indicating the sixth day.
Am sechsten Tag der Woche entspannte er sich.
On the sixth day of the week, he relaxed.
sechsten identifies the specific date in a month.
Sein Geburtstag fällt auf den sechsten April.
His birthday falls on the sixth of April.
sechsten qualifies the noun 'Buch' indicating its position in a series.