Das Jahrhundert hat mit großen Veränderungen begonnen.
The century began with great changes.
Im nächsten Jahrhundert wird vieles anders sein.
In the next century many things will be different.
Note
The article is part of the word: das Jahrhundert. That way you learn the gender with it.
Remember das Jahrhundert for good. ripiti brings the word back just before you forget it, with these sentences. Free, no account needed, works offline.