This is the 614th most frequent Lithuanian word.
renginių
"Renginių" means "events" in English.
The word 'renginių' here is the genitive plural form of 'renginys' (event), and it modifies 'daug,' which often requires genitive case when expressing quantities.
Mano mieste vyksta daug renginių vasarą.
In my town, there are many events during the summer.
'Renginių' here indicates possession and is used as the genitive plural form to denote 'of the events,' describing the organization.
Mūsų renginių organizavimas turi būti kruopštus ir gerai suplanuotas.
Our events' organization must be thorough and well-planned.
'Renginių' in this sentence is again in the genitive plural form, describing the type of calendar—specifically an events calendar.