LyX ⇒ How to change Lyx’s “fixed names” such as Chapter,Index???

[Bjorn21]

How to change Lyx’s “fixed names” such as Chapter, Index, Contents, Figure, Index ect....
only the fixed names, not the style.

[Maksi]

They are not LyX’s “fixed names” but the document classes’ “fixed names”. For many of them exist language files to change the names when not writing English papers. Maybe there exist some packages or commands out there, that can easily change the names, but I do not know of them. As far as I can remember, there is some kind of \renewcommand with which it could be possible. I have only read a few introduction books into LaTeX and they did not cover these aspects (they usually cover always the same, old and somewhat outdated stuff).