These are endings only for adjectival declansion, OG for genitive masculine singular, after soft consonants it becomes EG (dobrog, vruceg...) OJ is the ending for dativ and locative feminine singular (dobroj, vrucoj..), OM is the noun ending for instrumental both masculine and feminine singular (bratom, sestrom) and adjectival ending for dative and locative masculine singular, after soft consonants it becomes EM (dobrom, vrucem...)

I will try to answer, but maybe it would be easier if we had some sentences. -og and -eg are suffixes for genitive and accusative (acc just for living beings) . It is in use for, masculine and neuter singular. for pronouns and adjectives Ex.:Mog/dobrog/čijeg muža/djeteta (my/good/who's husband/child, of my/good/who's husband/child) -oj is for same for feminine. Ex.:Tvojoj/dragoj/čijoj? prijateljici (your/nice/who's? friend, to your/nice/who's? friend - om and -em is a prefix for instrumental. For singular and for all geneders