It cannot be changed. The expression comes from the idea that water that has fallen over a dam cannot be brought back again.

VOA: special.2009.05.10

Public officials recognize that social media has changed the way people communicate.

VOA: special.2009.09.14

But the turkey-growing industry has changed that.

VOA: special.2010.05.28

"The thing is that consumers' or the way they are buying has all changed already.

VOA: standard.2009.12.20

Much has changed since that time. Sobriety,his marriage to actress Nicole Kidman and the birth of their eight-month-old daughter,Sunday Rose, gave him a new perspective on life.

VOA: standard.2009.04.19

Suny and others point out that President Obama has changed his position.

VOA: standard.2010.03.19

But the secretary also said senior officials are aware that past efforts have failed, and he said it is not clear whether the view in Tehran has changed.

VOA: standard.2009.05.05

The United States has recently changed its Burma policy from isolating the military government to direct engagement in hopes that it will improve its human rights and allow for democracy.

VOA: standard.2009.11.08

a statistic that has not changed in 30 years.

VOA: standard.2010.06.04

In his commencement address, President Obama told the cadets he believes the nature of the war in Afghanistan has changed since it began in 2001, but that it is no less important today.

VOA: standard.2010.05.22

she says she has witnessed great change - much of it good But she noted that many important things have not changed, including the aims and values that inspired the United Nations Charter.

VOA: standard.2010.07.06