<synset id="r00181418" type="r">
<lex_filenum>02<lex_filenum/>
<word lex_id="0">as needed<word/>
<word lex_id="0">as required<word/>
<word lex_id="0">pro re nata<word/>
<word lex_id="0">PRN<word/>
<def>according to need (physicians use PRN in writing prescriptions)<def/>
<example>add water as needed<example/>
<synset/>