There are a few words used in German as a noun like in English, such as marriage and wedding.
Marriage, Wedding - Heirat, Hochzeit, Eheschließung and Vermählung
So in the cases above we're talking about the act of getting married.
Marriage - though can also be translated to Ehe.
Matrimony - Ehe
Now we're talking about the act of being married over a period of time.
Hope that helps.