Dragon Medical One (DMO) is designed to understand the majority of words that you dictate. It can sometimes, however, misinterpret or misunderstand words. This is usually due to the spoken form of the word differing from the written spelling of the word
An example of this would be when dictating for certain doctors' names (e.g. Dr Hsi, Dr Nguyen, etc.)
If you are finding that there are particular words Dragon is consistently getting wrong, it is recommended to add these words to your vocabulary.
For words that you have added to your vocabulary that are still being dictated incorrectly, see this additional article for other potential causes.