If you want to pass a variable, you have to define this variable with xsl:param element. : parameter « XSLT stylesheet « XML Tutorial

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2. XSLT stylesheet
3. parameter

File: Data.xml
<?xml version="1.0" encoding="utf-8"?>
<data>
    <number>1</number>
    <number>3</number>
    <number>4</number>
    <number>17</number>
    <number>8</number>
</data>
File: Transform.xslt

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet
      version="1.0"
      xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="/">
      <TABLE>
        <xsl:for-each select="//number">
          <TR>
            <td>
              <xsl:choose>
                <xsl:when test="text() mod 2">
                  <xsl:apply-templates select=".">
                    <xsl:with-param name="type">odd</xsl:with-param>
                  </xsl:apply-templates>
                </xsl:when>
                <xsl:otherwise>
                  <xsl:apply-templates select="."/>
                </xsl:otherwise>
              </xsl:choose>
            </TH>
          </TR>
        </xsl:for-each>
      </TABLE>
    </xsl:template>
    <xsl:template match="number">
      <xsl:param name="type">even</xsl:param>
      <xsl:value-of select="."/>
      <xsl:text> (</xsl:text>
      <xsl:value-of select="$type"/>
      <xsl:text>)</xsl:text>
    </xsl:template>
</xsl:stylesheet>
Output:

<?xml version="1.0" encoding="UTF-8"?><TABLE><TR><td>1 (odd)</TH></TR><TR><td>3 (odd)</TH></TR><TR><td>4 (even)</TH></TR><TR><td>17 (odd)</TH></TR><TR><td>8 (even)</TH></TR></TABLE>