de8fd92a_Advanced_Typography_tables__Reading_support
[0] 7 [name] contextual positioning [Writing support] These may be created with the Element->Font Info->Contextual command [Reading support] 
This sub-table allows the font designer to control the positioning of glyphs when they occur within a specific string (or class of strings). For instance this table could say "when you see a digit followed by the string "th" then raise the "th" into a superscript position"
Advanced Typography tables
Reading support