The Brief: Mx is a gender-neutral honorific like Mr. or Ms.
Mx is a title or honorific that doesn’t specify a gender. Commonly pronounced like “mix,” Mx was introduced in the 1970s as an alternative to Mr., Mrs., Miss, or Ms.
The title can be used by people who are nonbinary, who don’t wish to disclose their gender, or to refer to someone whose gender isn’t known.
Mx is not a pronoun like they/ze/xe/she/he, but a prefix to add before someone’s last name in order to address or refer to them more formally. The honorific is widespread in the United Kingdom where it’s accepted in many government and business documents, and relatively less common in the United States.
Example: “Mx Cohen will be fashionably late to the party.”