Or they can transport heat from an external source of power and manipulate it to cool a surface.

FORBES: The Trillion Mile-Per-Gallon Engine

In the simplest terms, an API is a set of code conventions which programmers can use to interact with an external data source or web service.

FORBES: With All Content Moving Mobile, Karen McGrane Writes, The API's The Thing

The engineers found a way to kick-start a radio-frequency device wirelessly using an external power source initially, but running the device afterward on the output of power generated by the inner ear.

WSJ: Harnessing Energy From the Body to Power Devices

Capturing great audio with an external microphone and adding a light source to improve the picture are all important too.

FORBES: Connect

It may be that, as capitalism makes us wealthier and we can buy what we desire, we can no longer blame an external situation for our misery and are forced to realise that our unhappiness has its source in our own minds.

ECONOMIST: Social insecurity