Is there such a thing as ADD without hyperactivity and is it something serious?

My son has been diagnosed with ADHD,which stands for "Attention Defficit Hyperactivity Disorder". ADD stands for "Attention Defficit Disorder".They are both stemmed from the same disorder. ADD means without the hyperactivity. ADD itself is far more uncommon.Both disorder's are serious and require support. If it is you or your child that is experiencing these difficulties,treatment and support are the best answer. Yes, there is, and I have it. In recent years you'll hear people refer to ADHD and not ADD, and I think this is unfortunate, for there are definitely people who don't have hyperactivity but have all the other symptoms. The prior post said that it's much less common than ADHD, and I'm not sure this is true. More likely, people with ADD don't get diagnosed because they're not doing things to draw attention to themselves. I wasn't diagnosed until I was 20. ADD is also more common than ADHD in girls.