US dictionary-maker Merriam-Webster has redefined the word ‘marriage’ to include gays and lesbians.

The definition of the word now says: “The state of being united to a person of the opposite sex as husband or wife in a consensual and contractual relationship recognised by law,” but adds the term also applies to “the state of being united to a person of the same sex in a relationship like that of a traditional marriage”.

The company said it had introduced the change in 2003, before gay marriage was allowed in any state, but said no one had noticed the change until conservative website World Net Daily reported it this week.

In response to a reader’s query on the political motivations for the change, associate editor Kory Stamper said: “We often hear from people who believe that we are promoting – or perhaps failing to promote – a particular social or political agenda when we make choices about what words to include in the dictionary and how those words should be defined.

“In recent years, this new sense of ‘marriage’ has appeared frequently and consistently throughout a broad spectrum of carefully edited publications … Its inclusion was a simple matter of providing our readers with accurate information about all of the word’s current uses.”