To join together in a federation, or to organize separate groups into a united system while keeping them somewhat independent.
Third-person singular present tense of 'federate,' from Latin 'foederare.' The verb form emerged in English in the late 1700s as nations began forming federal systems.
When Switzerland 'federates' its cantons or the EU federates member states, they're literally saying 'we're making a treaty to stay together'—the word still carries that ancient idea of binding together through agreement.
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