.LEX File

The lex file extension is commonly used for lexicon files. These files usually serve same purpose as Dictionary  or Vocabulary files - they store words or phrases that can be used in a program, typically for spell-checking.

These .lex files are used in numerous programs, like Adobe software, Microsoft Windows, Microsoft Office but in different formats.

How to open:

Usually, you can import lexicon files to their original programs only.

How to convert:

Sometimes users can export or transform lexicons / dictionaries between various formats.