Icons can help to quickly find a common feature without reading text. There are a few universal icons, many users learned; like speech bubble for chat, pen for edit, or trash for delete something. But many icons just don’t work without explanatory text.
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Don't invent icons. If you have to think for a long time about which icon you could use, it's a sign it won't work without text. In this case, make sure to use text beside or instead of the icon.