Dumtaxat is a bad word. Does anyone even know what dumtaxat means? Right at this very moment, I do. I write this so I don't forget the glorious lucid splendour of this instant in time.
Dumtaxat means "when it comes to."
Dumtaxat libros, lego "Familiam Romanam."
Dumtaxat holera, nulla amo.
Dumtaxat "dumtaxat," nemo scit quid significet.
Dumtaxat pulchritudine, Elizabeth Taylor fuit optima femina.
Dumtaxat is something you say when you want to say "exactly this much." Which is how it somehow means both "not more" and "not less."
Volo elephantos dumtaxat duos.
Consul Romanus habet potestatem dumtaxat annuam.
Dumtaxat can be used to specify what kinds of things you're talking about. It's like combining the above two meanings.
Boves dumtaxat grandes ducit ad campum, i.e. "He leads the cows (the big ones, specifically) to the field.
Non dumtaxat is "not only."
Non discipuli dumtaxat, sed etiam magistri non intellegunt "dumtaxat."
Non "dumtaxat" dumtaxat, sed etiam "quin," "quippe," et "quominus" non intellegunt.