- Not one of a pair, as a vein or muscle; occurring singly.
- An unpaired anatomical structure.
- An azygous part, as a muscle, vein, etc.
- In <xref>anatomy</xref>, a <xref>structure</xref> that is <xref>unpaired</xref>. This is relatively unusual, as most elements of anatomy reflect <xref>bilateral</xref> <xref>symmetry</xref>.
- occurring singly; not one of a pair