Add definitions for "measure" and "color"

The justiciation section uses these typographical terms, so it would be
make it easier for the reader to have short defintions of these terms at
the beginning of the section.

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@@ -757,9 +757,10 @@ <h3>Notes, Links, …</h3>
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-    <p>Of the four basic justification methods (flush left, flush right, justified, and centered), justified is the most challenging, as it requires changing the widths of the lines to a pre-defined measure.</p>
+    <p>Of the four basic justification methods (flush left, flush right, justified, and centered), justified is the most challenging, as it requires changing the widths of the lines to a pre-defined measure. <span class="qterm">Measure</span> refers to the width of a column of text. In a justified paragraph the width of all the lines should be the same as the paragraph’s measure (except, of course, the list line).</p>
     <p>In Arabic there are six mechanisms for changing the width of a line of text. Each one has its limitations and considerations on when and how it can be applied. Furthermore, different typographers and calligraphers have divergent preferences for these mechanisms.</p>
-    <p>These mechanisms are not exclusive. Quite the contrary, they are  commonly used simultaneously to produce better justified paragraphs. Combination of these mechanisms is discussed in <a href="#h_combination_of_the_mechanisms">Combination of the Mechanisms</a>.</p>
+    <p>An important factor in the application of these mechanisms is they success in creating an even <span class="qterm">color</span>. The color of the text refers to the amount of ink/blackness used to print or show a block of text. Color describes the density of the text against its background. Poorly justifying paragraphs can create uneven distribution of color.</p>
+    <p>These mechanisms are not exclusive. Quite the contrary, they are commonly used simultaneously to produce better justified paragraphs. Combination of these mechanisms is discussed in <a href="#h_combination_of_the_mechanisms">Combination of the Mechanisms</a>.</p>
 
     <section id="h_adjusting_inter_word_spaces">
       <h2>Adjusting Inter-Word Spaces</h2>
@@ -770,7 +771,7 @@ <h2>Adjusting Inter-Word Spaces</h2>
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       <p>A minimum width is defined for how much the space can be shrunk, because putting the words too close to each other creates aesthetic and legibility problems.</p>
       <p>Stretching the space too wide is also undesirable, but is utilized as a last resort when it is not possible to use other solutions to make fully justified paragraphs. In some applications a maximum width for the inter-word space is defined as a soft limit (compared to minimum width which is a hard limit). Reaching the maximum width makes the software to try to use other solutions for justification. If no other solution could yield the required result, the software would fall back to inter-word spacing and stretch the space past the maximum width.</p>
-      <p>Depending solely on this mechanism for aligning lines in a justified paragraph can lead to unpleasant results, such as rivers (multiple stretched spaces appearing vertically close to each other and forming a white gap inside the paragraph) and uneven distribution of spaces between different lines. Hence, typographers generally use other mechanisms as well to minimize the effect of adjusting inter-word spaces.</p>
+      <p>Depending solely on this mechanism for aligning lines in a justified paragraph can lead to unpleasant results, such as rivers (multiple stretched spaces appearing vertically close to each other and forming a white gap inside the paragraph) and uneven distribution of color in the paragraph. Hence, typographers generally use other mechanisms as well to minimize the effect of adjusting inter-word spaces.</p>
     </section>
 
     <section id="h_adjusting_intra_word_spaces">