to put something together with something else so as to increase the size, number, amount, etc.

to put numbers or amounts together to get a total

He knew how to add and subtract.

If you add all these amounts together you get a huge figure.

to say something more; to make a further remark

‘And don't be late,’ she added.

I have nothing to add to my earlier statement.

He added that they would return a week later.

‘The hotel is child-friendly,’ she said, adding that special rates apply to children.

to give a particular quality to an event, a situation, etc.

The suite will add a touch of class to your bedroom.

The Easter Festival added a new dimension to Salzburg's musical life.

LEARNit Dictionary