Braille definitions

Contraction:   The generic term for a braille sign that represents a group of letters or a whole word.
Contractions can occupy one or more cells.

Groupsign:      A contraction that represents a group of letters within a word.

Wordsign:       A contraction that represents a whole word.

Shortform:      A contraction where a word has been specially abbreviated in braille.

Upper sign:     A sign that contains a dot 1 or a dot 4.

Lower sign:     A sign that contains neither dot 1 nor 4.

Strong sign:    A sign that has dots in the top AND bottom rows, PLUS dots in the left AND right sides of the cell.