This question is related, but is not a duplicate, of Why do some words have "X" as a substitute?.

I have noticed that a few nouns can be significantly abbreviated with an "x" at the end. Some examples come to mind:

  • Transmit → Tx
  • Receive → Rx
  • Passengers → Pax
  • Tickets → Tix

There are likely others in existence I'm not aware of. Most abbreviated nouns ending in "x" seem to be used only as technical jargon (in this case, Fax, Fax, Transportation, Entertainment, respectively). What is the history of using "x" at the end of a word to severely shorten it? And, does the usage of "x" in this context have a single word to describe it?

  • Wiktionary has some information and additional examples about "-x" as an abbreviation: en.wiktionary.org/wiki/-x#Suffix_4. – geoff Mar 8 '17 at 20:54
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    Note that X is often used to mean "trans-", as in "Xmit". For "Tix", though, the reason probably is simply the sound similarity. – Hot Licks Mar 8 '17 at 21:06
  • X is also used to stand for cross; e.g., LX = lacrosse. There is no special word for abbreviations or initializations ending in X or any other letter AFAIK. It's all part of an inclination to shorten, to leave out what is already known--e.g., here, the OP, ELL. Note that in entertainment FX (not Fax) stands for effects, as in special effects. Also, Rx also means prescription; most acronyms and abbreviations have multiple meanings depending on context. – Xanne Mar 8 '17 at 21:47
  • I've always understood pax to stand for (paying) Passengers and (prepaid) Passes in the UK bus industry. In which context the x could be interpreted as a "wildcard" symbol covering both -ssengers and -sses. – FumbleFingers Mar 8 '17 at 23:07
  • Pretty sure this is a dup, even including the comment about "trans", but I don't have the time to search for the duplicate. – Drew Mar 9 '17 at 2:49

The letter "X" has long been used as a place-holder.

It was once standard for illiterate persons to sign legal documents with an "X".

Mathematicians use the letter "x" quite often as a place-holder.

For example, a mathematician might write, "Ɐ x, y, z ∈ ℝ, (x = y) ⋏ (y =z) ⟹ (x = z)"

It is standard to use an "x" to mean, "replace the x with some other string of symbols".

It is a convention.


In these cases X marks an abbreviation. Passengers becomes PAX, transmission becomes TX and so on.

This method of abbreviation for Passengers existed in the 1940s according to the comments in another article at this site: What does "pax" mean in the context of the apartment rental?.

  • 2
    In your first sentence, you restated what OP already knows. He's not asking what it means; he's asking: 1) why is "X" used for such abbreviations, 2) what's the history behind this usage (partly addressed), and 3) is there a single word to describe this usage? – AleksandrH Mar 8 '17 at 21:43
  • I reinforced the answer that OP gave himself; the word is "abbreviation". I provided some history. The "why" of abbreviation seemed self-explanatory given the resultant context. – Mike C Mar 8 '17 at 23:16
  • 1
    Yes, but why an X and not a Z for example? – Jim Mar 9 '17 at 4:25

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