Do I have to sell a stock to take a loss as in

Pat,
Generally speaking, yes you need to sell a stock in order to claim the loss for tax purposes and get any benefit.

However, I noticed that you have posted this question within the IRA section of the website. If we're talking about assets that you hold inside of your IRA, you do not get to claim a tax loss for declines in value, regardless of whether they're held or sold. For IRAs, your losses are effectively recovered because you only pay taxes on the future on what you actually withdraw (so if the value goes down before you withdraw, you'll never have to pay taxes on the growth in the first place).

I hope that helps a little!