I. Kiến thức liên quan
II. Giải thích idiom "a while back/ago"
Mang nghĩa "thời xưa, thuở xưa"
=At some point in the past.
- I bought this dress a while back but have never had a chance to wear it.
- I ran into Barbara a while back but didn't get her new address
- John wrote me a while ago about his new baby.