Marriage has been redefined to be gender-neutral in the 13th edition of Chambers Dictionary.
The dictionary now describes the institution as, "the ceremony, act or contract by which two people become married to each other."
The dictionary, first published in 1872, has also changed its definitions of husband and wife in order to reflect the change in the law in some jurisdictions.
Husband is now defined as "a man to whom someone is married," and wife is "a woman to whom someone is married."
Further words and phrases were added to Chambers Dictionary's latest edition, including sexting—sending explicit text messages—and YOLO, short for "you only live once."
According to Chambers, a word must demonstrate a "lasting influence on a language in order to avoid short-lived or faddy expressions being admitted."
Last August, the Macmillan Dictionary redefined the word "marriage" to include same-sex couples.
The dictionary's definition of the institution is now "the relationship between two people who are husband and wife, or a similar relationship between people of the same sex."
Macmillan's editor-in-chief said the organization was monitoring changes to the use of "husband" and "wife" to see if it would change those words as well.
Editor Michael Rundell said: "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."