The present article considers why Plato, in definitional conversations, finally don’t give a definitive answer to the question which is introduced in this class of conversations, and why these conversations are ended to aporia. For this purpose, first, we seek the etymology of this term, and then, it is concluded that, aporia means a trouble, in which the characters of the conversations, in finding answer of question, get themselves. Then. It is shortly considered that whether or not the aporia is the result of the method used in this class of conversations, i.e. elenchus. Moreover, several options are proposed in relation to the interpretation of aporia. In the final analysis of aporia, it is expressed that this situation is a reflection of the intellectual and philosophical situation in Greece, which Plato echoes in the definitional conversations.