Abbrevs have properties, some of which influence the way they work.
You can provide them as arguments to
manipulate them with the following functions:
Return the property prop of abbrev, or
nilif the abbrev has no such property.
The following properties have special meanings:
nil, this property marks the abbrev as a system abbrev. Such abbrevs are not saved (see Abbrev Files).
nil, this property should be a function of no arguments which returns
nilif the abbrev should not be used and
nil, this property indicates that the case of the abbrev's name is significant and should only match a text with the same pattern of capitalization. It also disables the code that modifies the capitalization of the expansion.