Hi Satish, it would be very helpful if you post a picture. In general I do not know if there exists a sharp demarcation line between them as the parent genera of Mokaras (Vandas, Arachnis and Ascocentrum) are all similar plants. One cultural difference I have opserved is that Mokaras are very fast growers as compared to Vandas, they tend to be more leggy and you can see the Arachnis like characteristics. They are much more floriferous as compared to atleast the vandas that I have. And when in flower you can definitely be sure.