Here is a vocabulary set with Buddhist culture related words and expressions

Buddhist culture Sri Lanka

පන්සල (Pansala) 
විහාරය (Viharaya)

we go to the temple on poya day (full moon day)

අපි ‌‌‌පෝයට පන්සල් යනවා - Api poyata pansal yanawa

පෝයට - poyata = පෝය දවසට - poya dawasata = on poya day

Full moon day - Every full moon day is a holiday in Sri Lanka and it's a special day. Every full moon day has a different specialty. Most Buddhist people celebrate this day by following Buddhist teachings.

පෝය දවස - Poya dawasa 
පසලොස්වක ‌පෝය දවස - pasaloswaka poya dawasa

Observing five precepts - Five precepts are the kind of guidelines that Buddhist lay people observe. They abstain from killing beings, stealing, sexual misconduct, telling lies, and taking intoxicating drinks and drugs.

පන්සිල් සමාදම් ‌වෙනවා - Pansil samadam wenawa

සිල් රකිනවා - Sil rakinawa ( keeping precepts without braking)
සිල්වත් ‌‌කෙනා - Silwath kena (The person who keeps precepts honestly)

Kandy Dalada procession (Dalada means a Tooth relic of the Buddha)
This event is celebrated annually in July or August.

නුවර දළදා ‌පෙරහැර - Nuwara Dalada perahera
also known as Nuwara perahera or Esala perahera 

Nuwara - Kandy city
Perahera - Procession