What describes a form that serves to express or indicate possession?

The term that appropriately describes a form that serves to express or indicate possession is "possessive." In English grammar, possessive forms are specifically used to show ownership or relationship between a noun and another noun. For example, in the phrase "the dog's bone," "dog's" is the possessive form that indicates the bone belongs to the dog.

The concept of possessiveness can manifest through possessive nouns (like "dog's," "children's," or "boss's") as well as possessive adjectives (like "my," "your," "his," "her," "its," "our," and "their"). This reflects a relationship of possession or ownership, making "possessive" the most fitting choice for this description.

While pronouns can also indicate possession (like "mine" or "yours"), they often serve broader functions in a sentence, and adjectives describe qualities or states rather than ownership. Articles, on the other hand, are used to define a noun as specific or unspecific, such as "the" or "a," without indicating possession. Therefore, "possessive" is the most direct and precise answer for describing a form that indicates possession.