The relationship between aperture-body resonance (ABR) and transmission-cavity resonance phenomena is discussed. From the viewpoints of both the equivalent circuit representation for transmission resonance condition and the funneling mechanism, the ABR and the TCR are essentially the same to each other. The common features of them are thought to be a general description for the transmission resonance phenomenon associated with aperture coupling problems. The ABR concept is extended to aperture coupling problems of various structures. Two types of transmission cavity, which can be used as the TCR structures, are also considered. Discussion is given on the role of the cavity in the aperture-coupled transmission cavity structures in the light of the TCR.