Roots constitutes the nuclei (or core) of all words. There may be more than one root in a single word, e.g. 'blackbird', 'catfish', and 'he-goat', and some roots may have unique occurrences. For example, the unique element 'cran-' in 'cranberry' does not constitute the nucleus of any other words, but it occurs in the positions occupied by roots; cf. 'redberry', 'blueberry', 'blackberry', and 'strawberry'.
- Nida (1949), Pag. 82