Questions & Answers about Sertifikat je na platformi.
Because after na when it means a fixed location, Serbian uses the locative case.
- Base form: platforma = platform
- Locative singular: platformi
- So: na platformi = on the platform
This is very common:
- na stolu = on the table
- na slici = in/on the picture
- na platformi = on the platform
So platforma is the dictionary form, while platformi is the form required by the preposition here.
It is locative singular.
The noun platforma is a feminine noun, and in the singular locative it becomes platformi.
In this sentence:
- na
- locative = location, meaning on / at
- na platformi = on the platform
A useful thing to remember is that some Serbian noun forms can look identical in different cases. platformi can also be dative singular in other contexts, but here it is locative because it follows na and expresses location.