I.R.I.S. Readiris 14 for Windows User Guide - Manual (Page 50)

Readiris TM 14 – User Guide
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Recognizing Western words in Cyrillic and Slavic languages
and in Greek
When you are processing Cyrillic, Slavic or Greek documents that
also contain "Western" words written in the Latin alphabet - such as
proper nouns, then it is recommended to select one of the available
Language pairs.
Language pairs are always combined with the English language and
are available for Russian, Byelorussian, Ukrainian, Serbian,
Macedonian, Bulgarian and Greek.
To select a Language pair:

Click the down arrow right of the Main list.

Then select the required language pair.
Example
Speed vs. Accuracy
In Readiris Corporate you can choose whether to favor recognition
speed over accuracy and the other way around.
Tip: when you are processing low-quality images, it is
recommended to set this feature to accuracy. This yields markedly
better results.