This is the 7783rd most frequent Swedish word.
ty
"Ty" means "because" or "for" in English.
Here, 'ty' is used as a conjunction meaning 'because' or 'for', introducing the reason for the sentiment expressed in the main clause.
Jag är glad idag, ty solen skiner.
I am happy today, for the sun is shining.
The word 'ty' functions as a conjunction, explaining the cause for the action described in the main clause.
Han valde att stanna hemma, ty han kände sig sjuk.
He chose to stay home, for he felt sick.
In this context, 'ty' introduces the reason behind the action stated in the preceding clause, which is the arrival of spring.