In America, a bed suitable for a single person (child) to sleep in is known as a twin bed, whereas in England it is a single bed.

Any ideas on why it is called a twin bed in America?

  • 2
    In the US, we do have a bed size called "super single" (which I had in college). It is longer than a twin though.
    – Kosmonaut
    May 30, 2011 at 17:42
  • 2
    @Kosmonaut: I've never heard the term "super single". The mattress size popular in college dorms is "extra-long twin".
    – Marthaª
    May 30, 2011 at 21:16
  • @Martha: Well, it is listed among the other sizes on Wikipedia. I never claimed my college's bed size was the most popular. It is just where I know the term from.
    – Kosmonaut
    May 30, 2011 at 21:23
  • Twin size beds are the same size as a Single, but come in pairs, thus the reason for naming them Twin.
    – Joe R.
    Sep 25, 2012 at 3:17
  • 2
    I always thought it was because we couldn't count.
    – Sven Yargs
    Mar 8, 2013 at 4:33

6 Answers 6


Twin bed is either of a pair of matching single beds ready to be joined to another twin bed to create twin beds. The word simply describes a bed which is stackable with another bed. A single bed isn't stackable, at least not the way you'd want it to.

UPDATE according to what John Y commented:

Well, wikipedia says:

U.S. terminology refers to a twin bed to mean what is known as a single bed in other countries, whereas other countries understand twin beds to be two single beds in the same room.

While wiktionary says:

twin bed (plural twin beds): Either of a pair of matching single beds.

Oxford dictionary says:

one of a pair of matching single beds, particularly in a hotel or guest room intended for two people.

So to sum it up, and now correct me if I'm wrong:

1 bed (US): twin bed
2 beds (US): twin beds

1 bed (UK): single bed or a twin bed if it belongs to a pair of beds
2 beds (UK): twin bed or twin beds

Therefore twin bed is ambiguous, unless the dictionaries are wrong.

  • 4
    This answer might be helped by citations. I am having trouble visualizing the way the component single beds are supposed to be joined or stacked. (For one thing, "joining" to me implies horizontal abutment while "stacking" implies something vertical, like a bunk bed, or some kind of crazy Princess-and-the-Pea arrangement.) Finally, it's wrong to say "Americans don't call single beds twin beds", because they (we) very plainly do, correctly or not.
    – John Y
    May 30, 2011 at 20:49
  • @John Y: Some twin bed frames have bedposts that are high enough that they can be stacked (see bunkbedscentral.com/main/…). They can also be joined side-by-side (with a thick enough mattress pad, and covered with double-bed sized sheets) to act as a double bed.
    – Jay Elston
    May 30, 2011 at 23:39
  • @Jay Elston: Thanks for the information, though that serves to add a little more confusion regarding double beds, because there is a bed size called "double" which is clearly much smaller than twice a single or twin. (To the naked eye, two North American twin beds side by side look very much like a king.) See Kosmonaut's excellent Wikipedia link on bed sizes in the main comments to this question.
    – John Y
    Jun 2, 2011 at 5:24
  • So then why does a "Double" size bed exist?.. Twin sounds ambiguous.
    – Joe R.
    Sep 25, 2012 at 3:01
  • I thought I would mention that I posted another answer that gives some more detail in layman's terms about your answer.
    – user189910
    Nov 4, 2017 at 1:59

Small cot-sized beds are often found in pairs: in barracks, dormitories, prisons, hospitals, children's rooms, and other places. Perhaps such beds were frequently referred to as "twin beds" formally or informally at the time that bed sizes were being standardized, and furniture manufacturers just decided to keep the name that everyone had been using for that size of bed anyway.

So why are they called "twin beds" even when they don't appear in pairs? It may be something of a backformation: if two such beds are twin beds, obviously one such bed must be a twin bed.

  • 4
    I have always supposed that it was a back formation from hotel parlance, but the examples of the phrase in the OED suggest that it is in reference to the sleeping arrangements of married couples: twin beds versus a double bed.
    – Colin Fine
    May 31, 2011 at 14:50

In the 1950s, a single was as wide as the average person's shoulders. A twin was a single & a half. A double was two singles. A queen was a single & a twin. A king was 2 twins (or 3 singles). Nowadays, the single is forgotten, so everyone is confused. When I was a child in the 1950's, my bed was a twin and you could put two first graders in it side by side. My best friend had a single bed, so when I slept over at her house, I slept in her bed and she slept on the floor.

  • 1
    This description makes the most sense. It's the first time I have ever heard of a "twin bed" in the singular, I have always heard of "twin beds" which are two identical single beds, often laid side by side, sharing the same floor.
    – Mari-Lou A
    Aug 10, 2017 at 4:30
  • This also helps explain the origin of the 'double' / full size, which presumably was twice the width of a 1950s-era 'single' bed. Sep 3, 2023 at 6:57

I sell beds in the UK, and the sizes that we have are small single bed which is 2' 6" wide and 6' 3" long; we have large singles which are 3 feet wide and 6'3" long; and these beds can all be joined together with what's called zip and link, where the bases bolt together and the mattresses zip together. We have a small double, 4 ft wide and the same length as singles; a double bed which is 4' 6" wide, same length; a king size bed which is 5ft wide and 6' 6" long; and a super king which is 2 x 3' 6" beds that zip and link together, but you have to have custom made bedding fit the super king. That's the UK system.

  • This is not what the OP asked.
    – fev
    Dec 29, 2020 at 15:36
  • Shows how specifying definitions refine standard dictionary definitions. Dec 29, 2020 at 16:19

Double or Full is larger than a twin (single) and smaller than a queen. Double means two people (double) can sleep on it if need be and the term FULL I think is because it is a full sized bed, not a kids single bed, or twin.... lol 2 twin beds side by side IS a King Sized bed. I think the term TWIN refers to the variations in which it can be used... it has a "twin" to make a King, a "twin" to make bunk beds, so if a child is part of a twin set..... Identical, etc., THAT person would refer to themselves as a twin.


This a layman's addition to RiMMER's answer.

Think of twin shorthand for twinned twins and double shorthand for double-sized.

Double beds are used for partnering bed space (hence their usage for romantic couples, close siblings, owners and their pets, etc)

Twin beds are used for increasing living-space density. Traditionally, twinned twins are 2 beds separated by a walk-space in the same room, but they have a generic definition which is:

Twinned twin beds are 2 beds using the same living space. [see RiMMER's answer]

This living-space factor has made twin beds not only popular, but useful in prisons, dormitories, and barracks, and it is the standard bed size for bunk beds.


Think of it this way, you don't give a married couple twinned twin mattresses, and you don't give prisoners double-sized mattresses (dropped soap-bars would be a problem)

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