(By Matthew S. Dryer): "This map shows information regarding definite articles. For the purposes of this map, a definite article is a morpheme which accompanies nouns and which codes definiteness or specificity, like ‘the’ in English. This is a somewhat broader use of the term definite article than is common, since it includes (i) affixes on nouns that code definiteness; and (ii) demonstratives, if those demonstratives are used as markers of definiteness. In many languages, words that are demonstratives, either in the sense that they can be used deictically with an accompanying gesture or in the sense that they exhibit a distinction in terms of distance (as in the contrast of this and that in English), are also widely used in contexts where English would use a definite article rather than a demonstrative."
Like the Grammaticon's definition, Dryer's includes affixal articles, and he includes both definite and specific articles. He also includes forms that are elsewhere used as demonstratives ("deictically with an accompanying gesture"), but when they only mark definiteness, they are also articles.