Private’s documents, as linguistic representations, embody part of people’s lived experience and also contain elements of historical concepts. These documents have received far less attention from scholars of Iranian architectural history than official, royal, chancery, and similar documentary sources, largely because documents of everyday life seldom refer to monumental buildings or enduring urban complexes. Moreover, historical documents are most often consulted in architectural studies for the purpose of constructing historical narratives, whereas their linguistic features contain forms of architectural knowledge that are not narrative in nature. Overall, the aim of previous studies has not been to understand the process through which a mental concept is transformed into a linguistic reality, nor have these studies considered language in terms of its units and structures as part of their research process. None of these studies has sought to examine how architectural categories are understood, organized, and constructed in documents, or to demonstrate how such conceptual structures can represent part of society's understanding of architectural categories. The present study aims to identify the linguistic structure underlying the understanding and representation of the category of architecture in Qājār-period documents. To this end, it employs concepts from structural semantics and subsequently interprets the findings in light of conceptual history. The study addresses two questions: How do these documents approach the category of architecture from the perspective of structural semantics? What new insights do they provide into the popular understanding of the category of architecture during the Qājār period? The research adopts a qualitative approach with content analysis method. A corpus of seventy-six private documents related to Shiraz during the Qājār period was examined in the archives of the National Library and Archives of Iran and the Women's Worlds in Qājār Irān Digital Archives. In the first stage, all documents were examined in their entirety. The words related to the category of architecture were then extracted from the content component of each document as the primary data. Since the objective was to identify the relationships among words, their frequency of occurrence was not considered a criterion for analysis. In the next stage, five principal categories were identified within the documents. By determining the position of the elements of each category along the syntagmatic axis and their alternatives along the associative axis, it became possible to examine the relationships among these elements on the basis of concepts drawn from structural semantics. To reconstruct the concept of the category of architecture, this study draws upon a network of concepts and lexical items that appear in the documents around the subject of the building. This network is the product of syntagmatic and associative (paradigmatic) axes arising from the positions occupied by these concepts and lexical items. This section is referred to as the synchronic reconstruction of the conceptual structure of the category of architecture, which serves as a substitute for the semantic field in conventional approaches to conceptual history. Since the majority of the documents examined in this study date from the final decades of the Qājār period, the saddle period, understood here as the interval between the Qājār period and the present, serves as the temporal horizon. This section of the study adopts a diachronic approach. The analysis revealed a process of the establishment and determination of the category of architecture, comprising: (1) establishment, (2) individuation, (3) attribution, (4) determination, and the identification of associated attributes. These findings were interpreted through two dimensions—establishment and determination—which demonstrate: the primacy of space over the building; the construction of the category of house on the basis of divided and undivided property (shaped by exchange value and the divisibility of the building); the definition of a building's limits through adjacent properties and a site-oriented perspective (based on an individual's position within the building); the attribution of buildings to persons and to the city; and the naming of buildings according to their attributes or characteristics. The status of space vis-à-vis the building, as reflected in the tripartite distinction among “land,” “building,” and “space” in Qājār architectural knowledge, no longer exists today. The determination of a building's boundaries through adjacency, based on a topological understanding that takes the individual's position within the building as its point of departure and relies on the sun's movement and the direction of the qibla for orientation, represents another conception of the determinative domain of the architectural category. Thus, understanding the architectural category through the documents reveals complex layers involving people, the city, and other buildings, which differ from the contemporary understanding of the building as a whole or as a legal and artistic entity. This study focuses exclusively on Shiraz and the Qājār period. It is hoped that future researchers will examine the category of architecture in documents from other periods and geographical regions of Iran, thereby contributing to a fuller understanding of what is referred to as Iranian architecture and its history.