The /ð/ sound is spelled with <th>. The /h/ sound is spelled with <h>.
This is a contrast between a voiced dental fricative and a voiceless glottal fricative. Although both sounds may occur medially after prefixes, as in methinks or behind, the only observed pairs occur initially. The separate sounds may be a problem for learners, but the contrast is fairly infrequent.
The mean density value is 0.9%. The list makes 19 semantic distinctions, a loading of 95%.
that hat thee he their hair theirs hairs their Herr them hem then hen thence hence there hair there Herr they hay this hiss thither hither though ho though hoe those hoes thou how thy hi thy hie thy high
John Higgins, Shaftesbury, November 2010.