It includes all who have a deep interest in something or some activity.

VOA: special.2009.05.17

She says people might have difficulty completing an activity if they cannot expect some kind of reward in return.

VOA: special.2009.09.29

Some areas have banned this activity.

VOA: special.2009.06.16

Some estimates suggest species extinction because of human activity is about 1,000 times faster than the natural rate of loss.

VOA: standard.2010.01.31

"I think the most difficult thing will be to be separated from the people that I am used to, and leaving behind some of the habits - all our activity will be directed towards a certain goal."

VOA: standard.2010.06.02

"I think it's only been since the Iranian Revolution that the United States has been the 'Great Satan.' And there was always a suspicion that the British were behind the scenes, even if the United States was more upfront involved in some kind of activity that was seen to counter Iranian national interests,".

VOA: standard.2009.07.02