The “fourth sector” is an emerging sector of the economy which consists of “for-benefit” organizations that combine market-based approaches of the private sector with the social and environmental aims of the public and non-profit sectors. Source: www.fourthsector.net

We will see the emergence of a fourth sector of the economy, interacting with but separate from governments, nonprofits, and for-profit businesses. The rise of that sector is likely to reshape the future of capitalism…
Source: Heerad Sabeti, Harvard Business Review