Creating a new or derived recognition language is similar to editing a user pattern.
Click Tools > Options and click the Languages tab. Here is a screen shot of the languages editor menu:
If your document uses multiple languages, you can select from the 192 languages that are offered by ABBYY
If your document contains characters in addition to what is found in these languages, you can select New in the Languages pane. Choosing this option will allow you to create a new language. It can be completely new or can be used in conjunction with a language (and related dictionaries) that exists in ABBYY. Your "new" or "derived" language will be based off of an existing language whose characters will already be included.
In ABBYY, you can select up to 1000 characters, including mathematical operators and other symbols.