This is the 708th most frequent Catalan word.
tren
Train.
Here, the root 'tren-' appears in 'entrenant', which means 'training' and refers to preparing for an event.
En Jordi està entrenant fort per al campionat de natació.
Jordi is training hard for the swimming championship.
In this case, 'tren' is used metaphorically in the expression 'tren de vida' to refer to the way or pace of life.
Aquest tren de vida no és sostenible a llarg termini.
This pace of life is not sustainable in the long term.
In this context, 'tren' refers to the literal vehicle used for transportation.