This is the 131st most frequent Vietnamese word.
tuần
"Tuần" means "week" in English.
In this sentence, 'tuần' means 'week' and refers to the regular time interval used with 'mỗi' (each).
Tôi đi chợ mỗi tuần.
I go to the market every week.
Here, 'tuần' is used in the sense of a measurement unit (tael).
Cái bánh này giá một lạng một tuần.
This cake costs one ounce per tael.
In this sentence, 'tuần' refers to a past week with the context specified by 'vừa rồi' (last).