Being scared to look stupid has kept a lot of smart people quiet.

The fear is not of being wrong, it is of being seen being wrong, and it is strongest in people who have been praised for being clever. If your standing depends on knowing things, every question becomes a confession. So the clever ones sit quietly through explanations they did not follow, and the gap widens while the reputation stays intact.

Ask the thing you think you should already understand, this week, in front of people. Use plain words and do not preface it with an apology. The relief in the room will tell you how many others were sitting on the same question.