NEW YORK -- The word "amnesty," at the core of the debate over a proposed immigration overhaul, has been a volatile, politically charged term throughout its history, often applying to acts hailed by supporters as magnanimous and assailed by critics as weak-kneed.

It's a word with flexible meanings. There were sweeping amnesties after the English and U.S. civil wars; nowadays the term is sometimes used when authorities invite the public to turn in unregistered guns or overdue library books without penalty...

"An amnesty differs from a general pardon in that the latter simply relieves from punishment whereas the former declares innocence or abolishes the crime," the Encyclopaedia Britannica says...

President Andrew Johnson's 1868 declaration directed at Confederate war veterans is perhaps the most prominent amnesty in U.S. history.

President Carter's pardon of Vietnam War draft evaders following his inauguration in 1977 is sometimes described as an amnesty, but it did not declare innocence...

The concept of amnesty dates at least to ancient Greece. In England, a general amnesty was offered as part of the restoration of the monarchy in 1660. South Africa used the term during the 1990s, when its Truth and Reconciliation Commission, despite criticism from two flanks, sought a public accounting of abuses committed during the era of White-minority rule...

This isn't the first time amnesty has been a focal point in wrangling over immigration.

A 1986 law signed by Ronald Reagan established a one-year amnesty program for illegal immigrants who'd been in the United States at least four years. An estimated 2.7 million people took advantage of the provision.