Ok, so I am a very educated person (will soon (if things go well in the next year) have a Ph.D. in physics), but sometimes when having conversations I cannot say a word that I know and want to use in a sentence. It is very frustrating and very hard for me to move on when the problem comes up. The word seems to be on the tip of my tongue,. I can describe what the word should mean, just cannot say the word. I can be speaking very eloquently, making a formal argument and this pops up and destroys my credibility. I don't really see any sort of pattern to when it occurs. I don't believe I have had any great head trauma; well, I have had a few minor concussions in my life, but nothing very serious. By the way, I am young. 25 years old. It is not alzhiemers. Does any one else ever experience this? Is it normal?