Abbrevs can also have global definitions that are active in all major modes. The same abbrev can have a global definition and various mode-specific definitions for different major modes. A mode-specific definition for the current major mode overrides a global definition. You can define Abbrevs interactively during an editing session. You can also save lists of abbrev definitions in files and reload them in later sessions.
Some users keep extensive lists of abbrevs that they load in every session.
A second kind of abbreviation facility is called the dynamic expansion . Dynamic abbrev expansion happens only when you give an explicit command and the result of the expansion depends only on the current contents of the buffer. See section Dynamic Abbrev Expansion . Defining an abbrev, so it will expand when typed. Viewing or editing the entire list of defined abbrevs.