<p>This research draws upon the concept of multiple meanings of form and the multi-layered connections between inside and outside to develop a theory from case studies. This exploration aims to elucidate the theoretical framework based on various levels of form within a place, from a phenomenological perspective. The levels of form (i.e. Spatial limitation, spatial penetration, and spatial representation) emerged through a complex interplay of inside and outside. The fundamental question guiding this research is: How does the language of form in the association between appearance and meaning, develop transactions between inside and outside in apartments? The research employed qualitative case studies. As a result, the language of form emerges at different levels: (1) Micro level: It is characterized by the dominance of spatial penetration, which connects the form to humans; (2) Mezzo level: It is characterized by the dominance of spatial limitation, which connects the form to itself; and (3) Macro level: It is characterized by the dominance of spatial representation, which becomes more apparent in the proximity of the form to other forms. The language of form encompasses the <i>relationships</i> between the inside and outside, covering morphological aspects, the <i>interactions</i> between the inside and outside, addressing physiological aspects, and the <i>transactions</i> between the inside and outside, focusing on ecological aspects.</p>