Thing, object, article are comprehensive terms applicable to whatever is apprehended as having actual, distinct, and demonstrable existence.
They vary, however, in their range of application.
Thing is the term of widest reference. In its most inclusive sense it need not imply direct knowledge through the senses but is equally applicable to something so known and to something the existence of which is inferred from its signs or its effects; thus, one thinks of the state, the church, literature, and the law as things rather than as ideas or abstractions; a friend’s affection is as real a thing as is his house or his hand; one distinguishes a word from the thing it names.
In somewhat more restricted use thing can denote specifically an entity having existence in space or time as distinguished from one existing only in thought or in still more restricted use an inanimate entity and especially a material possession as distinguished from living beings and especially persons.
Often the word is used idiomatically to mention without specifically identifying an item that cannot or need not be further identified or whose nature is implicit in the context; thus, in “be sure to wear warm things ,” clothing is implied; in “bring in the tea things ,” the necessary collection of dishes, implements, and foods is implied.
Occasionally thing may be used in reference to persons when contempt is expressed or derogation intended.
Object has for its primary implications externality to the mind or existence outside the observer. In philosophic and scientific use it is applied to something that is put before one as an entity capable of being seen, observed, or contemplated.
This basic implication of object is its chief distinction from thing when either word is used to denote something that can be perceived by one or more of the senses. For object in this, its ordinary sense, is applied chiefly to what has body and usually substance and shape.
Article is the most limited in its range of application, being used chiefly of objects that are thought of as members of a group, kind, or class.