- The innermost or first digit on the hind foot of certain mammals. The human hallux is commonly called the big toe.
- A homologous digit of a bird, reptile, or amphibian. In birds, it is often directed backward.
- The innermost of the five digits which normally compose the hind foot of air-breathing vertebrates; in man, the great toe. See cut under <internalXref urlencoded="foot">foot</internalXref>.
- The first, or preaxial, digit of the hind limb, corresponding to the pollux in the fore limb; the great toe; the hind toe of birds.
- The <xref>big toe</xref>
- the first largest innermost toe