This is the 441st most frequent Portuguese word.
sem
"Sem" means "without."
The word 'sem' is used here to indicate the absence of 'bringing bags' while going to the market.
Eu fui à feira sem levar sacolas.
I went to the market without bringing bags.
Here, 'sem' denotes the absence of 'eating' during the whole day.
Eles passaram o dia todo sem comer.
They spent the whole day without eating.
In this case, 'sem' signifies the absence or lack of 'my phone' as a condition for going out.