Civil union is a loosely defined term for a legally recognized partnership between two people that has similar benefits to marriage, but is not called marriage. It is not to be confused with civil marriage, which is simply any marriage performed by a government official without the need for a religious ceremony. Civil unions could be considered a broader form of domestic partnerships.
Support for civil union legislation has generally been related to the same-gender marriage debate. Opponents of same-gender marriage have sometimes proposed civil unions as a way to grant rights to same-sex couples while preserving a supposedly more traditional definition of "marriage", while some gay rights activists see civil unions simply as a more achievable compromise. However, most of the vociferous opponents of same-gender marriage are equally opposed to civil unions.
There is also some support for civil unions from groups that are simply uncomfortable with the religious connotations of "marriage" and want to enforce a clearer distinction between church and state in this area.
Vermont remains the only state to have civil unions. Some states have domestic partnership benefits, or reciprocal benefits; an increasing number of states such as Ohio and Nebraska have amendments and/or a Defense of Marriage Act which ban civil unions along with marriage and domestic partnerships. Massachusetts is currently (May, 2004) the only state to legalize same-gender marriage.