The /s/ sound is spelled with <s> or <c>. The /j/ sound is spelled with <y>. Notice the variable pronunication of year leads to pairs with sear and sir.
This is a contrast between a voiceless sibilant fricative and a voiced palatal semivowel, and can only occur initially. It does not cause problems.
Interesting pairs include:
The mean density value is 1.7%. The list makes 44 semantic distinctions, a loading of 67%.
C ye cell yell cells yells sack yak sacks yaks Sam yam sank Yank sap yap sapped yapped sapping yapping saps yaps sate Yate saucer sawyer saucers sawyers saw yaw sawing yawing saws yaws sawed yawed saw yore saw your saws yours sawn yawn say yea sea ye sealed yield sear year sear years see ye seer year sell yell sells yells selling yelling send yenned sends yens set yet sir year sirs years soak yoke soaked yoked soaking yoking soaks yokes soar yaw soared yawed soars yaws soar yore soar your soars yours sob yob sobs yobs sore yaw sores yaws sore yore sore your sores yours sooth youth soothes youths sot yacht sots yachts sou ewe sous ewes sou U sous U's sou you sung young surly yearly sword yawed
John Higgins, Shaftesbury, November 2010.