An electronic dictionary is a dictionary whose data exists in digital form and can be accessed through a number of different media. Electronic dictionaries can be found in several forms, including:
as dedicated handheld devices,
as apps on smartphones and tablet computers or computer software,
as a function built into an E-reader,
as CD-ROMs and DVD-ROMs, typically packaged with a printed dictionary, to be installed on the user’s own computer
as free or paid-for online products

 

OXFORD  DICTIONARY 

THESAURUS