Once your ad runs, you'l find the search terms that triggered your ad. You can find irrelevant search term that may trigger your Ads.
You can click on the keyword and add it to the list of negative keywords. Negative keywords can prevent your ad from showing to people who search for or browse content related to those words 68
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If you have something in mind about irrelevant keyword to your business, you can also add the negative keyword by clicking the Keywords tab on the left of the workspace, then Negative Keywords.