I'm not sure if this is too broad, but a character I have in my story is mute. This character only has three fingers on each hand. They probably aren't going to be able to use ASL or other sign languages because they only have the three fingers, so how would I create a unique sign language that only uses three fingers? The main problem I'm running into is numbers and letters. By three fingers, I mean three digits; i.e., two fingers and a thumb.

Edit: I just saw some issues people are having with my question. First and foremost, this character is not disabled. They have three fingers because I chose to give them three fingers. A sign language other than ASL or any other current sign language because, to my knowledge, most of those languages require five fingers, which my character lacks. As well, it is simpler to design a language which only uses three fingers for my purposes. Hope that clears things up!

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    $\begingroup$ I am curious: did you do any research into sign language and people with disabilities? For example, amputees or even people with bone / joint / tendon disorders? $\endgroup$
    – elemtilas
    Commented Apr 26 at 0:38
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    $\begingroup$ Great question! I did. Based on my own (very limited) knowledge of sign language, ASL specifically uses all five fingers of your hand, and it would be incredibly difficult if you only had, say, four fingers. Only having one hand is not a problem, as you would simply sign words that usually require two hands, e.g., "name" or "friend" with one hand. Or finger-spell. However, the character I have has only three fingers(two fingers + thumb) on each hand, and so it is basically impossibly for them to use ASL, BSL, etc. I'm not sure about problems with the hand itself. (cont). $\endgroup$
    – Talbot
    Commented Apr 26 at 0:42
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    $\begingroup$ I only asked because I literally typed that into Youtube and saw a video of a woman with only one hand talking about her sign language experiences! Also, when you get ready to delve into the mechanics of this language, you might want to ask questions over on our sister forum, Constructed Languages! $\endgroup$
    – elemtilas
    Commented Apr 26 at 0:45
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    $\begingroup$ I think your point about "combining letters" is spot on: the only correct answer to your question, and you actually answered it yourself!, is "people are geniuses at finding ways of coping with debilities". Your character will speak with a "very heavy accent" or "with a thick lisp" or something like that, but everyone will find a way to understand! $\endgroup$
    – elemtilas
    Commented Apr 26 at 0:54
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    $\begingroup$ Is there any particular reason you want to actually create the sign language your character will use instead of just describing it in broad terms? Creating a language is an extremely time-consuming endeavor (perhaps a hundred hours minimum), and if you're writing a traditional text-based story, your readers won't even be able to see any of what you've created. Maybe I'm misunderstanding you in some way. $\endgroup$ Commented Apr 26 at 11:07

5 Answers 5


Let's think from an information-theoretic point of view. Suppose there are around 30 letters that your character needs to represent (as is the case for many languages, including English (26), Greek (24), Cyrillic (33), etc. In order to represent $n$ different "states" (i.e. the different letters), you need at least $\log_2n$ bits of information. So if we have 30 letters, then we need $\log_230\approx4.90689\approx5$ bits.

Fortunately, your character actually has six bits: three fingers on each hand. Lowered means zero and raised means one. Fundamentally, there are thirty-two different possible combinations of raised or lowered fingers, which means that there is more than enough information in this system to represent an entire alphabet.

As for actually using this language, body language and/or any remaining few combinations (depending on your alphabet, it might not be any or it might be 8 for a Greek alphabet) can represent tone, and then your character just gets really good at raising and lowering fingers really fast. After years of having to communicate this way, your character is bound to get used to it, and anyone around them will eventually learn to read the sign language.

Numbers might be more difficult to represent. You could always spell them out, but that's not information-theoretically efficient. You also can't just make a gesture that says "I'm going to say a number real quick" and then hold up digits one-by-one, because you wouldn't be able to represent 7, 8, or 9. Spelling out the numbers might be the most intuitive way, but the information space is already pretty packed with letters...

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    $\begingroup$ Orientation (face foreward/back/sideways -or slanting combinations), hand coordination (touching one with the other) shake rhythms, touching the face-parts/body parts etc. all give an information space even larger. Plus, I'm not sure if the OP means three fingers (plus thumbs) or digits. $\endgroup$ Commented Apr 25 at 23:39
  • $\begingroup$ @controlgorup thanks for your contribution! I actually hadn't though about using both hands. $\endgroup$
    – Talbot
    Commented Apr 25 at 23:55
  • $\begingroup$ @Escapeddentalpatient. I will edit the question and clarify. $\endgroup$
    – Talbot
    Commented Apr 25 at 23:56
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    $\begingroup$ I must object to the terminology that you're using. You're describing a system for encoding written or spoken language. Sign languages are not systems for encoding written or spoken language; sign languages are languages. There's nothing wrong with systems for encoding written or spoken language, but please don't call them "sign language"! $\endgroup$ Commented Apr 26 at 11:00
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    $\begingroup$ What this answer is describing is known as finger spelling. It’s usable for unknown words, and commonly used for proper names, but no serious sign language consists solely of finger spelling. In practical terms this is like if you were speaking English by spelling out each individual word instead of pronouncing them phonetically, and it runs into a lot of the same issues that such methodology would. $\endgroup$ Commented Apr 26 at 17:37

Don't overcomplicate things.

ASL works by producing gestured that can be seen and distinguished from a small distance at a glance without counting how many fingers are up or down. You see a fist with two fingers sticking up left and right and you can associate this with the head of an ox, meaning horns or attack or pushing or whatever your unique sign language makes it mean.

If you hold up your hand palm up and create a gap between your middle and ring finger (the Star Treck Vulkan gesture) it looks similar enough to creating a gap between index and ring finger while the other fingers are missing, to mean the same thing. More complex meaning is added by holding this gesture in certain positions or moving this it in certain ways, where different movements have different meanings.

As for the numbers, use single fingers only for 1 2 3. Everything above that is a hassle to count and can lead to misunderstandings. A five could be signed by holding one finger horizontally, a ten by shaking one finger horizontally, twenty by shaking two fingers horizontally, etc. You can make up the most common gestures and combine them like Roman Numerals.

Letters are typically only used for things that don't have a defined gesture in a given sign language. That means you probably won't need them very often. It would probably be enough for your character to hold one hand up like a writing board and "writing" the letter with his other hand. Once they needed to write a word 3 times or more, they will find a gesture instead. The same applies to personal names.

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    $\begingroup$ This answer is the one that strikes at the core issue, which is not about information density but WHAT OTHER PEOPLE AROUND THEM SPEAK. If there already is a widespread sign language in your world, missing some fingers just means they'll have a (fairly small) speech impediment that might make things briefly complicated for communicating with strangers, but will essentially be invisible to anyone they communicate with on a regular basis. Fingerspelling is <10% of casual conversation, and most other signs will be obvious by context even when missing fingers might create ambiguity (which is rare). $\endgroup$
    – Jay McEh
    Commented Apr 26 at 13:04
  • $\begingroup$ Oops! I totally misread the question. Please disregard my previous comment. $\endgroup$
    – stux
    Commented Apr 29 at 15:32

With three fingers on one hand it would seem reasonable to produce up to 27 different signals using a trinary system, That is: three fingers, each open, curled, or closed, for 3*3=27 trinary states.

That would already provide enough states to spell in English (for example: 26 letters with a 'shift' character to switch to numbers and punctuation perhaps). Alternately, if the protagonist is Italian, then they only need 21 letter symbols, so have an extra 6 characters for punctuation. If they were Māori, then they only need 15 letters, so have 10 spare for 0..9 and two shift/special characters.

Alternately, if spelling out words seems too slow, they could use two signals in succession to 'spell' out up to 729 words (27^2). That would be more than enough for a small vocabulary synthetic language such as Toki Pona (<=137 words), and would probably be sufficient to 'encode' simple conversation in most languages (linguists suggest 700-800 common words is enough to get the majority of ideas across in most languages).

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    $\begingroup$ three fingers, each open, curled, or closed, for 3*3=27 trinary states. -this implies only fingers are used, but you can signal with he whole hand: palm up, palm down, fist up, fist down, chopping motion, placed a hand on different places on your chest/face tc. $\endgroup$ Commented Apr 26 at 7:47
  • $\begingroup$ Sign languages generally use symbols with meanings rather than spelling out a spoken language. $\endgroup$
    – arp
    Commented Apr 28 at 20:12

I have to agree with Elmy, don't overcomplicate things. ASL does not require a 5 fingered hand, and most sign languages have allowances for missing digits, so the actual number of digits on the hand is not normally significant. In most cases, a sign language is based on the positions of the hand and fingers (e.g. Straight from the palm, bent, intersecting with the other hand at multiple angles, etc...).


We've already got a real world parallel -- human spoken languages with a reduced phoneme count.

Languages like Inuktitut or Hawai'ian have fewer consonants, so words need to be longer to convey the same information.

Similarly, a sign language used by a species with only three digits would probably rely on longer sequences of simpler forms.

If your character is a disabled person trying to communicate in a world where sign languages are based on 5 fingers, then they will likely just muddle through as best as they can, and people will accept their imperfect signing, or not. After all, there are people with arthritis or other disabilities who use ASL every day. Some ways of adapting include picking different signs, signing more slowly, or altering gestures to be more recognizable. (I got some of this from https://www.lifeprint.com/asl101/topics/signing-with-physical-limitations.htm ).

After all, people with a lisp or speech impediment don't create their own languages, they just adapt as best as they can.


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