Dative preposition = an/am

I understand that “am” is a contraction for “an dem” which means you can write a sentence like “He is at the window” like “Er ist am Fenster”, as an alternative to “Er ist an dem Fenster”, which is practical when you apply the preposition “in” in the dative case form.

1. Can you do something similar with “der – masculine”? e.g.
English: He is at the bus
German: Er ist an dem Bus -> Is the contraction the same? am?
 
2. Can you do something similar with “die – feminine”? e.g.
English: It is at the box
German: Es ist an der Kiste - > what is the contraction here, if any?
 
3. Any contraction for “plural form”?

Hallo RexV!

Thanks for your question!

An + dem will always contract to am, whether dem is masculine or neuter - so yes, this is definitely possible!

There aren't any contractions between an and der or den, however, so none for the feminine or plural forms.

Be sure to keep in mind that the contraction am for an + dem is standard, so Er ist am Fenster shouldn't really be thought of as an alternative to "Er ist an dem Fenster"; rather, it is the preferred form (unless, as we've said before, dem is being emphasized for some reason). 

I hope that this is helpful!

Tschüss!

Liss