Editing Subalgebra (section)

=== Example ===
For example, the standard signature for [[group (mathematics)|groups]] in universal algebra is {{nowrap|(•,  <sup>−1</sup>, 1)}}. (Inversion and unit are needed to get the right notions of homomorphism and so that the group laws can be expressed as equations.) Therefore, a [[subgroup]] of a group ''G'' is a subset ''S'' of ''G'' such that:
* the identity ''e'' of ''G'' belongs to ''S'' (so that ''S'' is closed under the identity constant operation);
* whenever ''x'' belongs to ''S'', so does ''x''<sup>−1</sup> (so that ''S'' is closed under the inverse operation);
* whenever ''x'' and ''y'' belong to ''S'', so does {{nowrap|''x'' • ''y''}} (so that ''S'' is closed under the group's multiplication operation).