Braille is a system of raised dots arranged in cells. Any combination of one to six dots may be raised within each cell, and the number and position of the raised dots within a cell conveys to the reader the letter, word, number, or symbol the cell represents. There are 64 possible combinations of raised dots within a single cell. Due to the varying needs of braille readers, there are three different grades of braille.
In the first of the grades of braille, grade 1, each possible arrangement of dots within a cell represents only one letter, number, punctuation sign, or special braille composition sign — it is a one-to-one conversion. Individual cells cannot represent words or abbreviations in this grade of braille. Because of this grade's inability to shorten words, books and other documents produced in grade 1 braille are bulkier and larger than normally printed text. Grade 1 braille is typically used only by those who are new to learning the grades of braille, but as of the early 2000s a new movement was in place among elementary school teachers of braille to introduce children with sight difficulties to grade 2 braille immediately after teaching the basics of grade 1 braille.
Grade 2 braille was introduced as a space-saving alternative to grade 1 braille. In grade 2 braille, a cell can represent a shortened form of a word. Many cell combinations have been created to represent common words, making this the most popular of the grades of braille. There are part-word contractions, which often stand in for common suffixes or prefixes, and whole-word contractions, in which a single cell represents an entire commonly used word. Words may be abbreviated by using a single letter to represent the entire word, using a special symbol to precede either the first or last letter of the word while truncating the rest of the word, using a double-letter contraction such as "bb" or "cc", or removing most or all of the vowels in a word in order to shorten it. A complex system of styles, rules, and usage has been developed for this grade of braille.
The last of the grades of braille, grade 3, is essentially a system of braille shorthand. Because it has not been standardized, it is not used in publications. Instead, it is typically used by individuals for their own personal convenience. It contains over 300 word contractions and makes great use of vowel omission. In addition, the amount of spacing between words and paragraphs is decreased in order to shorten the length of the final document. It also sometimes substitutes combinations of punctuation symbols for words.