Macmillan Dictionary has become the first dictionary in Britain to revise the definition of marriage to include same-sex couples.

The change follows the Marriage (Same Sex Couples) Act for England and Wales receiving its Royal Assent on 17 July, after clearing the final stage in Parliament.

The definition of ‘marriage’ now reads: “The relationship between two people who are husband and wife, or a similar relationship between people of the same sex.” The second part of the definition is newly added.

The Guardian reports that Macmillan editor-in-chief Michael Rundell, said that the words ‘husband’ and ‘wife’, may also be changed, but that the dictionary would analyse their usage going forward.

“In a same sex relationship two men are probably not going to refer to themselves as ‘wife’, but if it’s two women, they might, so we need to keep an eye on that,” he said.

Macmillan currently defines wife as: “The woman that a man is married to”, and husband as: “The man that a woman is married to”.

“We have a corpus of two billion words, a huge collection of text including books, magazines and recorded speech, which we analyse in great detail to understand frequent and common usage,” Rundell said.

Oxford Dictionary also plans to change the definition of the word ‘marriage’ to keep in line with the passing of the recent same-sex marriage act in England and Wales, but said it would monitor the use of the word over a year before making the change. 

The OED said it “would continue to monitor the way in which the word marriage is used”, continuing that “dictionaries reflect changes in the use of language, rather than changes in law”.