English language is evolving—that’s a fact; some words have been coined and used for over 30 years but are just being reintroduced—that’s another fact. Mx, a gender-neutral honorific, is one of them.
It is pronounced /miks/ and supposedly coined from the initial letter of Mr/Mrs/Miss/Ms, and x (which is sometimes used for unknown).
*Note that Ms is used for any woman, regardless of her marital status( whether Mrs or Miss).
Known to have been in English lexicon since 1977, Mx was invented to be used before the surname or full name of people who do not wish to be identified by gender or who are not exactly male or female.
Currently, Mx is used officially in government corporations, other public service institutions, banks, etc. in the UK, but it is not so popular in America, though the first evidence of its usage was in an American magazine, Single Parent, about 40 years ago.
However, Mx is gaining popularity around the world and other speakers of English seem to be adopting or considering adopting it.
Moreover, you can find this word in the latest editions of Merriam-Webster Unabridged, Cambridge, Oxford and Macmillan dictionaries, etc.
So, to people who do not wish to reveal their gender or are not exactly male or female, Mx is dedicated.
Also read: Unforgiveness: not an English word?