The job of a translator can sometimes be rather treacherous when it comes to choosing the correct register, or level of lexicon, in a live, simultaneous translation.
Sometimes there are very precise words that could translate exactly what was said, but might be completely out of context, or even archaic.
The risk of falling into bombastic and stilted speech that is never used outside high-brow literary environments is great whenever a translator loses sight of the level in which the conversation is taking place, if he has fallen in love with words he may have learned in his language studies.
Take the following adverbs of place, for example: wherefore, wherein, wheresoever, whereof, etc. These are wonderful words that are elegant in their economy and precision. So, when a parent asks,
—Pero, doctor, ¿de dónde proviene la infección?
the translator may feel tempted to display his prowess by resorting to the aforementioned beautiful adverbs:
"But, doctor, whence did the infection come?"
Doubtful that clear communication will be achieved thus!
Or consider the colloquial phrase,
"I know what I'm talkin' 'bout!"
Its correct form in English is:
"I know whereof I speak!"
You may very well know whereof you speak, but the rest of the 21st Century English-speaking people might not.
For the patients' sake, choose your lexicon with care.