<p><font face="Arial"><strong>Nosology</strong> (from the <a title="Greek language" href="http://en.wikipedia.org/wiki/Greek_language" title="Greek language">Greek</a> &quot;<em>nosos</em>,&quot; &quot;disease&quot;) is a branch of <a title="Medicine" href="http://en.wikipedia.org/wiki/Medicine" title="Medicine">medicine</a> that deals with <a title="Classification" href="http://en.wikipedia.org/wiki/Classification" title="Classification">classification</a> of <a title="Disease" href="http://en.wikipedia.org/wiki/Disease" title="Disease">diseases</a>.</font></p><p><font face="Arial">Diseases may be classified by <a title="Etiology" href="http://en.wikipedia.org/wiki/Etiology" title="Etiology">etiology</a> (cause), <a title="Pathogenesis" href="http://en.wikipedia.org/wiki/Pathogenesis" title="Pathogenesis">pathogenesis</a> (<a title="Mechanism" href="http://en.wikipedia.org/wiki/Mechanism" title="Mechanism">mechanism</a> by which the disease is caused), or by <a title="Symptom" href="http://en.wikipedia.org/wiki/Symptom" title="Symptom">symptom</a>(s). Alternatively, diseases may be classified according to the <a title="Organ system" href="http://en.wikipedia.org/wiki/Organ_system" title="Organ system">organ system</a> involved, though this is often complicated since many diseases affect more than one organ.</font></p><p><font face="Arial">A chief difficulty in nosology is that diseases often cannot be defined and classified clearly, especially when etiology or pathogenesis are unknown. Thus diagnostic terms often only reflect a symptom or set of symptoms (<a title="Syndrome" href="http://en.wikipedia.org/wiki/Syndrome" title="Syndrome">syndrome</a>).</font></p><p><font face="Arial">Some of the earliest efforts at developing a classification of diseases began in the <a title="18th century" href="http://en.wikipedia.org/wiki/18th_century" title="18th century">18th century</a> with the <a title="Taxonomist" href="http://en.wikipedia.org/wiki/Taxonomist" title="Taxonomist">taxonomist</a> <a title="Carolus Linnaeus" href="http://en.wikipedia.org/wiki/Carolus_Linnaeus" title="Carolus Linnaeus">Carolus Linnaeus</a> and Francois Boissier de Sauvages, although <a title="Thomas Sydenham" href="http://en.wikipedia.org/wiki/Thomas_Sydenham" title="Thomas Sydenham">Thomas Sydenham</a>'s work in the late <a title="17th century" href="http://en.wikipedia.org/wiki/17th_century" title="17th century">17th century</a> </font> might also be considered a nosology.</p><p><font face="Arial">In the <a title="19th century" href="http://en.wikipedia.org/wiki/19th_century" title="19th century">19th century</a>, <a title="Emil Kraepelin" href="http://en.wikipedia.org/wiki/Emil_Kraepelin" title="Emil Kraepelin">Emil Kraepelin</a> and then <a title="Jacques Bertillon" href="http://en.wikipedia.org/wiki/Jacques_Bertillon" title="Jacques Bertillon">Jacques Bertillon</a> developed their own nosologies. Bertillon's work, classifying causes of <a title="Death" href="http://en.wikipedia.org/wiki/Death" title="Death">death</a>, was a precursor of the modern medical-billing code system, <a title="ICD" href="http://en.wikipedia.org/wiki/ICD" title="ICD">ICD</a>.</font></p><p><font face="Arial">The early nosological efforts grouped <a title="Disease" href="http://en.wikipedia.org/wiki/Disease" title="Disease">diseases</a> by their <a title="Symptom" href="http://en.wikipedia.org/wiki/Symptom" title="Symptom">symptoms</a>, whereas modern systems (e.g. <a title="SNOMED" href="http://en.wikipedia.org/wiki/SNOMED" title="SNOMED">SNOMED</a>) focus on grouping diseases by the <a title="Anatomy" href="http://en.wikipedia.org/wiki/Anatomy" title="Anatomy">anatomy</a> and <a title="Etiology" href="http://en.wikipedia.org/wiki/Etiology" title="Etiology">etiology</a> involved.</font></p><p><font face="Arial"><a idname="See_also" nameid="See_also"></a></font></p><h2><font face="Arial"><span class="editsection"></span><span class="mw-headline">See also</span></font></h2>

<li><a titlefont face="Differential diagnosisArial" ><a href="http://en.wikipedia.org/wiki/Differential_diagnosis" title="Differential diagnosis">Differential diagnosis</a></font></li> <li><a titlefont face="ICDArial" ><a href="http://en.wikipedia.org/wiki/ICD" title="ICD">International Statistical Classification of Diseases and Related Health Problems</a></font></li> <li><a titlefont face="Medical classificationArial" ><a href="http://en.wikipedia.org/wiki/Medical_classification" title="Medical classification">Medical classification</a></font></li> <li><a titlefont face="PathologyArial" ><a href="http://en.wikipedia.org/wiki/Pathology" title="Pathology">Pathology</a> (study of disease)</font></li> <li><a titlefont face="Category:DiseasesArial" ><a href="http://en.wikipedia.org/wiki/Category:Diseases" title="Category:Diseases">Category:Diseases</a> (Wikipedia's categorization of diseases)</font></li>

<p><font face="Arial"><a idname="External_links" nameid="External_links"></a></font></p><h2><font face="Arial"><span class="editsection"></span><span class="mw-headline">External links</span></font></h2>

<li><font face="Arial">Gordon L. Snider, Nosology for Our Day Its Application to Chronic Obstructive Pulmonary Disease, <em>American Journal of Respiratory and Critical Care Medicine</em> Vol 167. pp. 678-683, (2003). <a rel="nofollow" titlehref="http://ajrccm.atsjournals.org/cgi/content/full/167/5/678" class="external text" hreftitle="http://ajrccm.atsjournals.org/cgi/content/full/167/5/678" rel="nofollow">fulltext</a></font></li>