Definition of the Baader-Meinhof Phenomenon: a situation where something you recently learned about suddenly seems to appear everywhere.
You've probably noticed this in relation to a new word. You start to hear it all the time. This is true, not just in a second language you are studying, but in your native tongue when you encounter a specialized or abstruse word. Like abstruse.
This morning I realized the phenomenon hadn't happened to me in ages, almost a year and a half to be specific. The last such new word was "onboarding", a term which came up in the process of teaching a student who was looking for a better job as an HR professional. Does that mean I've quit learning new vocabulary? Not at all. I now have a student who plans to attend medical classes in 2023. In the past, I would have used "prone" and "supine" interchangeably to mean "lying flat". However, "supine" means specifically lying on your back (which I sort of knew but never thought about) while "prone" means specifically lying face down. I'm learning abstruse new words all the time, sometimes while searching for the simplest word to express an idea.
"Onboarding" stands out because my frequency-illusion experiences are now rare. Am I associating with illiterate people? Since many current acquaintances are teachers, I hope not! Have people suddenly started using a smaller vocabulary? Doubtful. So my brain must have quit latching on to a newly learned word, saying, "Hey, there it is again!"
I miss that.