the word is...

1. German: for "thought."

2. Physics & Philosophy: adjective for a type of experiment performed only in the mind. 

3. Computer Science: Gedanke Experiment (GE), pejorative for ill-thought-out, untested, argument or thesis.

4. "Die Gedanken Sind Frei" (My thoughts freely flower) is an old song of protest, referred to by a Free Software advocate, favoring free speech/thought.

5. Compiler: GEDANKEN (1970), a simple typeless language, in the tradition of LISP (lambda calculus).