Perhaps the reason that so many love the free math lessons at KhanAcademy.org is the way everything is explained. First the way things are said addresses people who think in different ways; this appeals to those not 'getting' the flat 'directions to do an operation' way of learning. These explain the 'why' behind the operation. Secondly, these lessons don't always assume prior math mastery and simple parts of the concepts are also explained. Those who find those bits boring and repetitive will have to just bear with those parts.
Watch this lesson from the beginning of algebra to see what I mean.
Perhaps also parents working with their kids on math homework or on homeschool lessons can learn something about how to explain math by listening to these examples. Consider this a mini teacher workshop on speaking math language. Watch a few of these, or however many you need in order to learn how math can be explained using different terms.
I have a feeling that a reason that math seems to be a struggle for parents to talk to their kids about is the parent is only speaking in ways that make sense to their own mind and they are not aware of the way their child's mind thinks enough to tune into it and change the communication style.
Actually that applies to many things in the parent-child dynamic ranging from simple power struggles to major issues. Tune in parents, then adjust what you to. Try to speak the language they understand.
Don't make a power struggle over trying to force your child to hear what you are saying in your language. If they just don't get it, they don't get it. Repeating things the same way over and over probably won't work. You are the adult, so choose be more flexible. Find where your words are not getting through, (which is a miscommunication on your part really, if anyone's looking for blame for the kid not getting it), then change what YOU say in order to get through to them so you know you are being heard.