Among the many statements that we usually come across, we will emphasize this one, common by the way:
Well, this one, like so many others, represents a typical example of communicative situations that have already crystallized in the over time, once uttered in an almost generalized way, but that represent a disagreement when it comes to language formal.
This time, we arrive at an important discussion: which one is correct?
When symptoms persist, the physician should be notified.
or
If symptoms persist, the physician should be notified.
To do so, it is enough to analyze that the "a", portrayed in the second alternative, represents a condition, perfectly materialized by:
If symptoms persist...
If symptoms persist...
On the other hand, the combination represented by “ao” denotes the meaning consistent with time, that is, when the symptoms persist... A fact that becomes proven through the following example:
As he approached, the boy showed interest.
As he approached, the boy showed interest.
Thus, such elucidations confirm that there really is a misunderstanding regarding the occurrence under discussion.
By Vânia Duarte
Graduated in Letters
Brazil School Team
Grammar - Brazil School
Source: Brazil School - https://brasilescola.uol.com.br/gramatica/ao-persistir-ou-persistir.htm