Can a Eurofighter 2000 trainer be converted to a combat capable Eurofighter 2000? It surprises me to see that in some aircraft inventory listings, a rather considerable percentage of combat aircraft are "trainer" versions.

E.g. https://en.wikipedia.org/wiki/Spanish_Air_Force#Current_inventory

For Spain, it is claimed they have 56 Eurofighter 2000, and 12 trainers. Somewhat similar numbers apply to their F-18 variants regarding combat aircraft and trainer aircraft.

I'm curious what the difference is between these Eurofighter 2000 combat vs. trainer aircraft. In particular, how much effort is it to make a trainer EF2000 combat ready? Perhaps they actually are combat ready? Surely there are some differences though, such as having two seats? What else?
From the Wikipedia page on the Eurofighter Typhoon, under Variants:


  The Eurofighter is produced in single-seat and twin-seat variants. The twin-seat variant is not used operationally, but only for training, though it is combat capable.


No source is cited for that claim, but it seems logical enough.