This sort of morphology stands against 'fusional' morphology, where it is hard to find sharp boundaries between morphemes and several bits of grammatical information are commonly included in a single morpheme. Adjectives and nouns, in particular, are hard to differentiate outside of specific instances of use. Consider the root sagdi 'old'. Moreover, there are no syntactic properties inherent to the root which lead us to classify it as one way or the other. The distinction between nouns and verbs is also not nearly as clear as what one finds in familiar Indo-European languages.
Many roots simply seem to be unmarked for word class.
One fascinating and understudied aspect of Tungusic comes from the realm of derivational morphology. In contrast, a language such as English allows limited derivation with numerals. Unfortunately, Tungusologists have not always been careful to identify how productive particular derivational morphemes are or the range of meanings they can have. Therefore, derivational morphology remains one of the largest unexplored issues of the Tungusic lexicon. There is variability in the number of cases that individual languages have, with the low end represented by the five of Manchu and the high end represented by Evenki with thirteen or so.