Difficulties of stating meaning also occur in the case of morphemes of unique environment, which are segmented off when an utterance has a unique residue after all morphemes have been divided off. In 'boysenberry', 'berry' is certainly a morpheme. Therefore, 'boysen' is also a morpheme, having as its meaning the differentia between 'boysenberry' and other 'berries'.Similarly, in 'there', 'then', 'thither', 'this', 'that', etc., we obtain […] a segment /ð/ with demonstrative meaning, plus various residue elements with unique meanings (/is/ ‘near’, /æt/ ‘yonder’, etc.). In 'where', 'when', 'whither', 'which', 'what', 'why', etc., we obtain an element /hw/ with interrogative (and in some linguistic environments, relative or resumptive) meaning, plus various second elements with unique meaning (/at/ ‘object reference’, /ay/ ‘reason’, etc.).
- Harris (1951), Pag. 192