diff --git a/guidelines/index.html b/guidelines/index.html
index 436f6305..a078a8c4 100644
--- a/guidelines/index.html
+++ b/guidelines/index.html
@@ -2975,10 +2975,10 @@ <h1 id="title" class="title">Web Content Accessibility Guidelines (WCAG) 2.2</h1
    
 </dd>
             
-            <dt class="new"><dfn id="dfn-perimeter" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">perimeter</dfn></dt>
+            <dt class="new"><dfn id="dfn-perimeter" tabindex="0" aria-haspopup="dialog" data-dfn-type="dfn">外周 (perimeter)</dfn></dt>
 <dd class="new"><p class="change">[New]</p>	
-   <p>continuous line forming the boundary of a shape not including shared pixels, or the <a href="#dfn-bounding-boxes" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-bounding-boxes-2" title="[New]">minimum bounding box</a>, whichever is shortest.</p>
-  <aside class="example" id="example-16"><div class="marker">例</div><p>The perimeter calculation for a 2 CSS pixel perimeter around a rectangle is 4<em>h</em>+4<em>w</em>, where <em>h</em> is the height and <em>w</em> is the width. For a 2 CSS pixel perimeter around a circle it is 4𝜋<em>r</em>.</p></aside>
+   <p>共有するピクセルを含まない図形の境界を形成する実線、又は<a href="#dfn-bounding-boxes" class="internalDFN" data-link-type="dfn" id="ref-for-dfn-bounding-boxes-2" title="[New]">最小境界ボックス</a>の、いずれか短い方。</p>
+  <aside class="example" id="example-16"><div class="marker">例</div><p>矩形を囲む 2 CSS ピクセルの外周の算出方法は、4<em>h</em> + 4<em>w</em> である。ここで、<em>h</em> は高さを、<em>w</em> は横幅を表す。円を囲む 2 CSS ピクセルの外周の場合は、4𝜋<em>r</em> である。</p></aside>
 </dd>