Abstract : We present an emotion ontology for describing and reasoning on emotion context in order to improve emotion detection based on bodily expression. We incorporate context into the two-factor theory of emotion (bodily reaction plus cognitive input) and demonstrate the importance of context in the emotion experience. In attempting to determine emotion felt by another person, the bodily expresson of their emotion is the only evidence directly available, eg, ''John looks angry''. Our motivation in this paper is to bring context into the emotion-modulating cognitive input, eg, we know that John is a generally calm person, so we can conclude from expression (anger) plus context (calm) that John is not only angry, but that ''John must be furious''. We use a well known interoperable reasoning tool, an ontology, to bring context into the implementation of the emotion detection process. Our emotion ontology (EmOCA) allow us to describe and to reason about philia and phobia in order to modulate emotion determined from expression. We present an experiment suggesting that people use such a strategy to incorporate contextual information when determining what emotion another person may be feeling.