The /ð/ sound is spelled with <th>. The /ʧ/ sound is spelled with <ch> or <tch>.
This is a contrast between a voiced dental fricative and a voiceless affricate, close together in the mouth. The contrast does not cause problems.
The mean density value is 1.4%. The list makes 15 semantic distinctions, a loading of 68%.
bother botcher bothers botchers breathe breach breathing breaching leather lecher leathers lechers leathery lechery teethe teach teething teaching that chat their chair theirs chairs there chair these cheese thine chine those chose thou chow with which with witch withies witches wreathe reach wreathing reaching
John Higgins, Shaftesbury, November 2010.