In answer to the obvious query: yes, I did indeed check the standard sources before I let that word pass. And I decided the standard sources need to be improved. Now I must agree we've lived all these years without feeling the need for yet another adverb that starts out with "there-". The O.E.D. lists 38 of them: thereabout, thereabove, thereafter, thereafterward, thereagain, thereagainst, thereamong, thereat, thereaway, therebefore, therebeside, thereby, theredown, thereforth, therefrom, therehence, therein, thereinto, there-nigh, thereof, thereon, thereout, thereover, therethrough, theretill, thereto, theretofore, theretoward, thereunder, thereuntill, thereunto, thereup, thereupon, thereward, therewhile, therewith, therewithal, therewithin But none of these works as a replacement for "therebetween" in either of the following two lines from my recent missive: the category whose objects are all Hilbert spaces that can be isometrically embedded in A and whose maps are all linear operators therebetween of bound at most 1. the subcategory of all closed subspaces of A and all inclusion maps therebetween. So why not shoot for 39? Best thoughts, Peter