The /ð/ sound is spelled with <th> or <the>. The /l/ sound is spelled with <l> or <ll>.
This is a contrast between a dental fricative and a lateral continuant, both voiced and fairly close together in the mouth. Although the individual sounds may not occur or may have restricted environments in many languages, the contrast does not cause problems.
Interesting pairs include:
Since /l/ is a fairly common sound while /ð is rare, the mean density value is low at 0.4%. The list makes 34 semantic distinctions, a loading of 65%.
bathe bail bathed bailed bathes bails bathing bailing booth buhl bothered bollard lithe lisle mother mullah mothers mullahs scathing scaling seethe seal seethed sealed seethes seals seething ceiling sheathed shield southern sullen teethe teal tether teller tethers tellers that lat thee Leigh thee lea thee lee their lair theirs lairs their layer theirs layers then Len there lair there layer these leas they lay thine line though lo though low those lows thy lie tithe tile tithes tiles with will withy willy withies willies Worthing whirling wreathe real wreathe reel wreathed reeled wreathing reeling wreathes reeels writhe rile writhed riled writhes riles writhing riling
John Higgins, Shaftesbury, November 2010.