The Nemeth Punctuation Indicator (Rule VI and Rule XVIII)

This page is about the use of the Punctuation Indicator and is not a complete introduction to the use of the punctuation marks themselves.


The rules of Nemeth require that the dot 4-5-6 Punctuation Indicator or PI precede certain punctuation marks in certain contexts. The main practical difficulty in applying the rules is the correct identification of context.

Rules apply to six lower-cell signs, the "six cells", that are used as both numerals and punctuation marks and also to the apostrophe.


This page addresses the rules for the use of the Punctuation Indicator (PI), dots 4-5-6. The Punctuation Indicator complements certain functions of the Numeric Indicator and is used primarily to ensure that the six physical cells which can be used as either numerals or punctuation marks in the same context are correctly identified as punctuation marks when that is their intended meaning. These rules are more easily applied if the punctuation marks are grouped into sets of symbols with similar behavior.

Although not considered as punctuation marks, rules for using the mathematical grouping symbols of Rule XVIII are included since they are used to transcribe print grouping symbols in both literary and mathematical contexts. (Note that all references to Rules, pages, and sections are to the 1972 Revision of the Nemeth Code.)

Grouping Symbols

It is easier to understand the rules for the PI by looking first at the use of grouping symbols. Nemeth does not used dots 2356 for parentheses as in literary braille. Rather, the special symbols listed in Rule XVIII are used to represent a variety of parentheses, brackets, and braces in all contexts.

These grouping symbols are considered to be mathematical symbols and not punctuation in Nemeth. Nonetheless, they are used to transcribe the corresponding print symbols in a literary context and require an intervening PI if followed by one of the six cells or by an apostrophe.

Since there is a distinction in the treatment of embellished and unembellished grouping symbols that affects the rules for the use of Letter Indicator, this distinction is mentioned here for consistency although it doesn't directly affect the rules for a PI. (See also the special considerations involving unembellised grouping symbols and the uses of the NI and the PI.)

In summary, the presence of a grouping symbol, embellished or not, does need to be considered when deciding about the need for a Punctuation Indicator because of its being a mathematical symbol:

When a Rule XVIII grouping symbol would otherwise immediately precede one of the punctuation marks in the special literary punctuation subset, then an intervening PI is always required. [This rule has the advantageous consequence that any numeral can be used immediately following a grouping symbol without requiring a preceding Numeric Indicator.]

Punctuation Marks Used in the Nemeth Code

Nemeth punctuation marks are used to transcribe punctuation in both literary and mathematical contexts. There are five sets of punctuation marks that each have their own associated sets of useage rules.

The literary punctuation marks that use the same six physical cells as certain Nemeth numerals.
There are six braille cells that are used as both punctuation and numerals in the same contexts in the Nemeth code. (The reason there aren't eight is that the literary comma is never used after a mathematical expression and Nemeth doesn't use the literary braille parentheses.) These braille cells thus each correspond to several semantic cells in dotless or extended braille. These six cells are grouped together because they are always preceded by a Punctuation Indicator in or immediately following a mathematical (not literary) context to distinguish them from the same physical cells being used as numerals.

  1. (dots 23) used as a semi-colon
  2. (dots 25) used as a colon
  3. (dots 256) used as a literary period (which is not the same physical cell used for the decimal point)
  4. dots (235) used as a literary exclamation mark (which is not the same physical cell used for the factorial sign),
  5. dots (236) used as an open double (left outer) quotation mark or as a question mark (which latter use is not the same physical cell as used for the omission symbol) [See also use of this cell as part of the symbol for an open single (left inner) quotation mark.]
  6. dots (356) used as a close double (right outer) quotation mark or as the first cell of the two-cell close single (right inner) quotation mark
The Apostrophe and the Single Quotation Mark

As for the apostrophe, while its use in text transcribed according to the Nemeth code follows the rules of literary braille, its use in a mathematical context always requires a preceding PI. (I believe this rule is to ensure the readability of this dot 3 cell and to avoid ambiguity.) However, the following ess (which is the only character that would normally follow an apostrophe in math) immediately restores the context to math.

Note that, in constrast to some print useage, the apostrophe and single quote are different characters in braille. The left single quote is (dot 6, dots 236) and the right single quote is (dots 356, dot 3). In the unlikely event that the left single quote were preceded by math context it would not require a PI because of the dot 6; the right single quote follows the same rule as the right double quote. However, both the single and double left quotes can require a following NI when preceded by a number.

The Literary Comma

The dot 2 literary comma must be used to transcribe commas used in literary contexts. This comma is never used in mathematical context and is thus never preceded by the PI.

The Mathematical Commas

There are two punctuation marks used to represent commas in mathematical contexts. One or the other of these commas must be used for transcribing commas within or immediately following mathematical expressions. They leave the context as math and don't require a preceding PI. However, the dot 6 mathematical comma is always followed by a space when used to transcribe a comma punctuation mark so the context following the space can be either literary or mathematical depending on the nature of the material transcribed.

The (dot 6) "comma" may also be used to group numerals in a long number; in this case it is never followed by a space and is a Rule II numeric symbol, not a punctuation mark.

Dual-use punctuation marks

The information here concerns the non-use of a PI with these marks and their effect on context. See the code book for additional rules regarding spaces with these items and the use of the long dash as a symbol of omission.

There are four punctuation marks, which have dot patterns that wouldn't cause problems in interpretation, that have dual use. When these punctuation marks are used in a text context, they generally leave the context as text and when used in a mathematical context, they leave the context as math. A PI is never used before one of the dual-use punctuation marks even though it is sometimes required after one of them as necessary to intervene before another punctuation mark. It is recommended that extended braille treat each of the dual-use punctuations marks as a pair of separate semantic cells in the two contexts.

When any of the dual-use punctuation marks are used in a math context and would then be immediately followed by one of the six cells that can be used as both numerals and punctuation, an intervening PI is required if the cell is meant as a punctuation mark. [Rule VI. Sec. 37xiv; Rule VI 38 iii.]

Although the hyphen used the same cell as the minus sign, the rules here only apply to its use as a hyphen.

Hyphen or en dash, (dots 36)
The rules for using the hyphen are somewhat inconsistent as they affect the use of PI, the NI, and the LI. A PI is needed for the somewhat unusual situation of punctuation immediately following a hyphen if the PI would be needed if the hyphen were not there; that is, if the previous context is mathematical, a PI is needed but if it is literary, a PI is not needed. [Rule VI 37xvii] This complements the rule that a number immediately follow a hyphen does not require a preceding NI where the previous context is mathematical [Rule II, 11d] but does where the previous context is literary [Rule II, 9f].
However, an LI is needed for an eligible symbol in contact with a hyphen.
Short dash or em dash, two repeated (dots 36)
The primary use of the short dash—as in this case—is to insert a parenthetical remark into literary material. The rules for the short dash are the same as for the hyphen.
Long dash, four repeated (dots 36)
The PI is not used after the long dash or ellipsis when the preceding context is clearly mathematical. [Rule VI 37 iv] The PI is used after the long dash when its occurs in a literary context or the nature of the context is in doubt. [Rule VI 38 iii]
Ellipsis, three or more repeated dot 3's
The rules for the ellipsis with respect to the use of PI are the same as for the long dash.

Using Punctuation in a Literary Context in Nemeth

Punctuation marks are used directly within a text (prose) context without ever causing a change in context. Also, these marks do not require a preceding PI in a literary context. (Click here for an example of the non-use of a PI before a colon.) However, any punctuation immediately following a grouping symbol requires a preceding PI no matter what the context is just before the grouping symbol.

The full literary punctuation set includes all punctuation marks and related symbols that can be used directly in a text context.

Although grouping symbols are considered as mathematical symbols in Nemeth, unembellished grouping symbols are nonetheless required to transcribe grouping symbols which occur in literary contexts in print. These will require an intervening PI when followed by punctuation marks transcribed with one of the special six cells. This is necessary to complement the rule that a numeral immediately following a grouping symbol does not require a PI.

Using Punctuation in a Mathematical context.

Whereas punctuation marks used in a literary context only require an intervening PI in the special case of a grouping symbol preceding particular ones of them, the PI is required on a more regular basis in a mathematical context. In fact, all of the punctuation marks except the mathematical commas and the dual-use ones will require an intervening PI following mathematical context and this useage has the side effect of changing the default context to text.

(Note that the required space following a mathematical comma has the potential for changing the context whereas the subscript comma always leaves the context as mathematical.)


A punctuation mark used on the baseline, whether or not preceded by a PI, always cancels subscript or superscript positioning so a baseline indicator is never used in this situation.

Last updated February 26, 2002.

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