This is the 635th most frequent Vietnamese word.
lâu
"Long" (in terms of time); "a long time."
The word 'lâu' is used to signify a long period since the last meeting.
Lâu không gặp, bạn khỏe không?
Long time no see, how are you?
The word 'lâu' is used to mean a long duration of time.
Tôi đã ở đây lâu rồi.
I have been here for a long time.
Although it sounds similar, in this case, 'lau' means 'to wipe' or 'to clean' in Vietnamese.