Learn Polish: Gdyby nie twój refleks, mógł zginąć. - If it weren't for your reflexes, he could have died.

The phrase gdyby nie (if it weren't for) is followed directly by the Nominative case. Even though the English translation uses a preposition, the Polish structure literally acts more like 'if twój refleks were not [present]'.

Why doesn't the second part of the sentence use the conditional form mógłby?

With modal verbs like móc (to be able to) and mieć (to have to / be supposed to), Polish often drops the conditional ending -by in the main clause if the condition is already clearly established by gdyby. Saying mógł zginąć is very natural and common here to mean 'could have died', though mógłby zginąć is also grammatically correct.

Why use zginąć instead of umrzeć for 'to die'?

Zginąć specifically refers to a sudden, tragic, or unnatural death, such as in a car crash or a similar accident. Because the sentence mentions quick reflexes saving the person, it strongly implies a sudden physical danger. Umrzeć is more general and is typically used for natural causes or illness.

The English translation says 'reflexes' (plural), but the Polish sentence uses the singular twój refleks. Is refleks always singular?

Yes, when talking about human reaction time, refleks is a singular, uncountable noun in Polish. It behaves exactly like the phrase 'reaction time' in English, which is why it takes the singular modifier twój rather than a plural form.