About the Use of the Verb ‘yertal’ (to go)

In Armenian, with the verb (երթալ) to go we use either a dative case noun, or an accusative case noun. If our intention of going is a location, we use an accusative case noun. and if our intention of going is to an event, we use a dative case noun. 

eg.

Ես դպրոց կ՚երթամ։ /yes tbrots gertam/

I go to school.

դպրոց is accusative

but

Ես հարսնիքի կ՚երթամ։ /yes harsniki gertam/

I'm going to a wedding. 

հարսանիքի is dative case. 

we cannot say հարսանիք կ՚երթամ, we must put ի at the end of the noun, to make it dative.