As, when, while dùng đồng nghĩa với although, but, seeing that
A. As có thể đồng nghĩa với though/although nhưng chỉ trong tổ hợp tính từ + as + chủ từ + to be/to seem/to appear :
Tired as he was he offered to carry her = Though he was tired he offered to carry her
(Mặc dù đã mệt anh ta vẫn...