The autocomplete ("Complete Selection") feature Ctrl-K (or F2 on Windows) works fine for functions and code input.
Is there a way to enhance it for text input?
Today’s standard (see e.g. OpenOffice etc.) is to autocomplete based on words already occuring in the text.
For text Mathematica will just display words from a (very simple) dictionary. If I type e.g. "Grav" it will show "Grave", "Gravy" etc. It does not even seem to know "Gravity" or "Gravitation" (despite these being common words and despite occurences in my text)

