But they also co-operate with each other (this is then called "synergy", and is the raison d'être for many of the mergers and acquisitions that they themselves put together for others).
The federal law includes a "good neighbour" provision, but it also emphasises the autonomy of the states.Some states have co-operated with each other, even without the federal government telling them to do so.
A sense of crisis has been gradually developing since the Democratic Unionists and Sinn Fein, the two parties which dominate the devolved administration, effectively stopped co-operating with each other on most issues.
There were long-term difficulties with the integration of the different ski areas; but once that had been achieved, the rich, former farming families who control the skiing co-operated with each other on a strategy to move Andorra up-market.
Although the EU probe focuses on the CDS market between 2006 and 2009, and although Markit denies any wrongdoing, the investigation may signal that regulators take an increasingly dim view of banks co-operating with each other, especially via a third party in which they have stakes.
"We agreed that we would co-operate with each other in dealing resolutely with North Korea," Mr Abe said.
Neighbouring forces such as Norfolk and Suffolk, and Beds and Herts, are co-operating with each other to save cash.
We have technology now to design networks of small intelligent units capable of competing and/or co-operating with each other on specified tasks and making decisions under conditions of uncertainty through a process of negotiation.
The use of multi-agent systems to model and to simulate real systems consisting of intelligent entities capable of autonomously co-operating with each other has emerged as an important field of research.
"It comes as no surprise that some of the [media] companies will sue and have sued, and I think ultimately there needs to be reasonable ways of operating with each other," he said, adding later that "I don't think the whole world is about videoclips".
These factors and the signaling pathways they affect often operate synergistically with each other, and with other molecules.
