css "word break" is not working when I use Korean

Question

I want to line break the tag with word. I used various css but it isn't working. I used "word-break: break-word" , "word-wrap:break-word", and "overflow-wrap: break-word". All of them not working. I want to know why. When I put Korean in the span tag, "word break" is not working. but when I put English in the span tag, It is working. This is React project. Thank you for helping me :)

<td style={{ position: 'relative'}}>
  <div style={{ display: 'flex', justifyContent: 'center', alignItems: 'center'}}>
    <span style={{ display: 'inline-block', width: '6.25rem', whiteSpace: 'normal', wordBreak: 'break-word'}}>유음의 단순화</span>
    </div>
</div>