Lesson 4.1: Variables
A variable is a quantity that varies in its possible value. Letters are usually used to represent variables in mathematical expressions. Grade 1 symbol indicators may be needed in simple mathematical expressions where letters stand alone or where the letters a through j follow numerals. Grade 1 mode is needed when the symbol could be misread as a grade 2 meaning or as a numeric meaning.
In the circumstance of a sequence of letters standing alone that could represent a shortform word, grade 1 mode must be turned on by the grade 1 symbol indicator or by the use of grade 1 passage indicators for the entire expression. The choice of grade 1 indicators will be determined by the presence of any additional items within the expression that require grade 1 mode. The preference is to use the grade 1 indicator that best preserves the mathematical expression without interruption.
In Example 1, the single letter n is used as a variable. The letter stands alone and also has a grade 2 meaning therefore the grade 1 symbol indicator is required.
In Example 2, the single letter a is used as a variable. The letter stands alone, however it does not have a grade 2 meaning. A grade 1 symbol indicator is not required.
In Example 3, a single letter is used as a variable. The letter does not stand alone, therefore it does not need a grade 1 indicator.
The numeric indicator turns on grade 1 mode. A lower-case letter a through j that immediately follows a number can be misread as a numeric meaning. The grade 1 symbol indicator is used to set grade 1 mode for the letter. The grade 1 indicator also turns off numeric mode.
An upper-case letter that immediately follows a number does not require the grade 1 symbol indicator. The capital indicator turns off numeric mode and prevents the letter from being misread as a numeral.
Variables in mathematical expressions should follow print for spacing and case. The capital letter indicator, dot six, is used before a single capital letter. A capital word indicator dots six, six, should precede an upper-case letter sequence that is used as a variable.
When a sequence of letters used as a variable could be read as a shortform, a single grade 1 symbol indicator is used. This turns on grade 1 mode for the first letter of the sequence, thereby separating it from its potential shortform word meaning.
The letters should be spaced as the symbols they represent in the mathematical expression.