What do you call the actual possession of land by someone claiming rightful ownership?

The term used to describe the actual possession of land by someone claiming rightful ownership is seisin. This concept is rooted in property law and refers specifically to the legal possession of a feudal estate. Seisin implies not only physical possession of the land but also the intention to own it. It encompasses the idea that the possessor has an interest in the property, which, in many legal contexts, can influence rights related to that property.

Seisin may be critically important in establishing one's claim to land, particularly in situations involving disputes over ownership or title. In historical contexts, having seisin would confer various legal benefits, such as the ability to transfer property or the right to utilize resources on that land. This makes seisin a foundational concept in understanding property rights and legal claims in real estate.

In contrast, the other terms operate in different legal contexts. A writ is a formal written order issued by a body with administrative or judicial jurisdiction. Trespass to try title is a legal action used to resolve disputes over property ownership but does not inherently refer to possession. Res judicata is a legal doctrine that prevents re-litigation of cases that have already been judged, which is not directly related to the claim of ownership of land.