The nucleus of a morphological construction consists of (1) a root or (2) a combination of roots (including possible nonroots attributive to respective roots). [...] In 'breakwaters' the nucleus 'breakwater' consists of two roots.
- Nida (1949), Pag. 83

Roots constitutes the nuclei (or core) of all words.
- Nida (1949), Pag. 82