1 about == more than or fewer / less than
He has been here for about 5 months.
2 具体数字+ or so == about - - -
He arrived five days OR SO ago.
3 more or less == somewhat
She arrived more or less disappointed,for there was no one to meet her at the airport.
3+3=6 -------Three plus three is six
3-3=0--------Three minus three is zero
3 X 3 = 9 ------Three times three is nine
3 / 3 == 1 -----Three divided by three is one.