For my own edification I need an answer.

The other night I was chatting with two friends and the question of hard water versus soft water came up. I used the phrase 'acid water' to describe 'soft' water, and they said, Oh, no, acid water is hard water.

So, have I been wrong lo, these many years? I'm aware that soft water isn't loaded with minerals thus sudses quickly while hard water tastes funny and doesn't suds easily. I also know that rain water is, by and large, soft. I know too that hardness is measured by ph, soft ranging to hard. But which is which? Alkaline versus Acid?

How do you define the terms and conditions?