Word / formMeaning / explanation
سَمِعَhe heard
مَسْمُوعٌheard.
عَلِمَhe knew
مَعْلُومٌknown.
مَسْمُوعُونَheard masculine plural entities, where that description fits the context.
مَعْلُومَاتٌknown feminine plural things; the word also conventionally denotes information.
The first two are masculine singular participles. The -ūna and -āt endings produce the regular masculine and feminine plural, though lexical usage may become more specialised.