Vowel /ɪ/ is here spelled <i>. The /ʊə/ diphthong is <oor>, <our> or <ure>. This dictionary has /bʊən/ as the only pronunciation of bourn (meaning stream or boundary). Other dictionaries give that as an alternative to /bɔn/, which would make the word a homophone of born, reducing the number of minimal pairs to 5.
The contrast is not a problem for any known group of learners.The mean density is insignifcant at 0%. There are 8 semantic distinctions, making for a loading of 86%, or 100% if bourn is excluded.
bin bourn bins bourns biz boors krill crewel krill cruel lid lured Liz lures mid moored Ms Moors
John Higgins, Shaftesbury, July 2014