This is the 775th most frequent Vietnamese word.
bức
The Vietnamese word "bức" can mean "picture," "painting," or refer to "sheet" (e.g., a piece of material) depending on context.
In this sentence, "bức" is used as a classifier for the noun "tranh" (painting).
Tôi đã treo một bức tranh mới trong phòng khách.
I hung a new painting in the living room.
"Bức" in this sentence functions as a classifier for the noun "thư" (letter).
Mẹ tôi đã gửi cho tôi một bức thư từ quê nhà.
My mother sent me a letter from home.
Here, "bức" is part of the adjective "bức bối," which describes a feeling of stuffiness or discomfort.