In both the phonologic and the morphologic analyses the linguist first faces the problem of setting up relevant elements. To be relevant, these elements must be set up on a distributional basis: 'x' and 'y' are included in the same element 'A' if the distribution of 'x' relative to the other elements 'B', 'C' etc., is in some sense the same as the distribution of 'y'.
- Harris (1951), Pag. 7