How does the definite article differ between Eastern Armenian and Western Armenian?

In the Armenian language, the definite article is expressed as -ə (after consonants) and -n (after vowels). While both Eastern and Western Armenian share these markers, they differ significantly in their application, particularly regarding the genitive case.1

In Eastern Armenian, the definite article is often omitted after the genitive. For example, pat-i can mean "of the wall," and pat-er-i can mean both "of walls" and "of the walls." Conversely, Western Armenian usage is more explicit, requiring the definite article to indicate the genitive definite. For instance, "of the wall" is bad-i-n and "of the walls" is bad-er-u-n, whereas the forms without the article (bad-i and bad-er-u) specifically denote the indefinite genitive.1

Additionally, Western Armenian may attach the definite article to other case forms where Eastern Armenian does not. A notable example is the ablative case: "from Armenia" is rendered as Hayastan-ê-n in Western Armenian (incorporating the -n article), while Eastern Armenian uses Hayastan-ic‘ without an article.1