理论上的英语

theory and practice 理论与实际它们是对应关系。因此Theoretically, practically也是对应关系不过实际上，最常用的还是in fact

从理论上来说，看来是可行的。It seems to work in theory.

in theory in fact

in theory,it seems workable .

理论: theory 理论上是如此。 It is so in theory 这种理论与已知事实不符。 This theory is at variance with the known facts