Toleration is "the practice of deliberately allowing or permitting a thing of which one disapproves. One can meaningfully speak of tolerating, ie of allowing or permitting, only if one is in a position to disallow”. It has also been defined as "to bear or endure" or "to nourish, sustain or preserve". Toleration may signify “no more than forbearance and the permission given by the adherents of a dominant religion for other religions to exist, even though the latter are looked on with disapproval as inferior, mistaken or harmful”.
There is only one verb 'to tolerate' and one adjective 'tolerant', but the two nouns 'tolerance' and 'toleration' have evolved slightly different meanings. Tolerance is an attitude of mind that implies non-judgmental acceptance of different lifestyles or beliefs, whereas toleration implies putting up with something that one disapproves of.
Historically, most incidents and writings pertaining to toleration involve the status of minority and dissenting viewpoints in relation to a dominant state religion. In the twentieth century and after, analysis of the doctrine of toleration has been expanded to include political and ethnic groups, homosexuals and other minorities, and human rights embodies the principle of legally enforced toleration.
Source: Wikipedia, "Toleration", available under the CC-BY-SA License.