This is the 277th most frequent German word.
jeden
The German word "jeden" means "every" or "each" (accusative singular masculine form).
'jeden Tag' is an accusative singular construction of 'jeder' referring to 'Tag' (day), denoting a repeated action every day.
Ich sehe jeden Tag den Sonnenaufgang.
I see the sunrise every day.
'Jeden Dienstag' indicates a routine action occurring each Tuesday, forming a standard expression for dates in accusative singular.
Jeden Dienstag gehen wir ins Fitnessstudio.
Every Tuesday we go to the gym.
'jeden meiner Freunde' uses 'jeden' as an accusative because of the verb 'lade ein', reflecting the individual friends invited.