This article aims to formalize abstract nouns with the suffix “-pen” in Rromani. The suffix “-pen” follows the lexemes of various word types, mainly adjectives, verbs, nouns and adverbs, prepositions, and a numeral. We have described this derivation phenomenon and formalized them on the NooJ platform with two methods: treating derivatives as lexical entries (“.nod file”) and describing them by derivational morphology (“.nof” file). As our next project, we would have to systematically examine all potential base words to test the third method (i.e., describing by productive morphology (“.nom” file) and irregular phenomena (e.g., phonetic variants) to complete the formalization on the NooJ platform.