This article introduces a cognitive model called the physiological = psychological model and discusses how one understands synesthetic expressions of language, e.g., warm color. It is argued that there are two major types in synesthesia: one is the type whose synesthetic mapping is based on the co-occurrence of the senses, and the other on the emotional similarity of the senses. As for the former, it is claimed that the strength of sensory relations in daily experiences determines what type of synesthetic combination is possible (interpretable), e.g., warm color vs. ??red temperature. As for the latter, it is argued that the interpretation of synesthetic expressions, such as fragrant music, is enabled by the synthesis of different emotional experiences.