> Prefer words to icons. Use only icons that are universally understood.
Underrated. Except for dyslexic people, and the most obvious icon forms, I am pretty sure most people are just better and faster at recognising single words at a glance than icons.
It varies, some applications - the ones that people spend their workday in - have specific iconography that is domain specific for that application.
A difference needs to be made between general public applications and domain specific employee applications. SAP is a great example of this. Of domain specific icons I mean, not of good UX design.
...except for HN "unvote"/"undown" feedback which is especially unfortunate due to the shared prefix. Every time I upvote something I squint at the unvote/undown to make sure I didn't misclick.
I am pretty sure icons are easier and faster to recognize, except when you make them (too) small. In particular, they probably are easier in the long run, as long as they don't change position. But in a context where things change or you need a lot of buttons, words probably win.
I'm somewhat dubious about that for icons with actual recognizable pictures, but a lot of icon attempts today are stylized to death, with just a line, bent and broken in a couple places and maybe if you're lucky juxtaposed with the occasional dot. If there's no text description even on mouseover (or touchscreen, with no cursor...) discovery is more or less trial and error (or perhaps more akin to Russian Roulette if the permissions involve being able to do real damage). Scratch your head and hope there are existing support questions searchable about what on Earth the programmer could have meant to convey...