Character entity references can also have the format &name; where name is a case-sensitive alphanumeric string. For example, Î» can also be encoded as &lambda; in an HTML document. The character entity references &lt; , &gt; , &quot; and &amp; are predefined in HTML and SGML, because, ,  and & are already used to delimit markup. This notably does not include XML's &apos; (') entity.
Lack of facial expression. Lack of facial expression: Introduction. An absence of expression on the face is medically called flat affect. In many cases, the face mirrors the underlying emotions, and the person has limited emotions or various emotional or psychological disorders.
Bell's Palsy. Bell's palsy causes paralysis or weakness of the muscles on one side of the face. It results from facial nerve paralysis that causes the affected side of the face to appear flat, expressionless, or droopy. Taste sensation and tear or saliva production can also be affected.