Dyad means two things of similar kind or nature or group and dyadic communication means the inter-relationship between the two; but in practice, this relationship refers to dialogic relations or face to face verbal communication between two persons involving their mutual ideas, thought, behaviour, ideals, liking and disliking and above all the queries and answers concering life and living in nature.A sudden communication between two persons in the street and not continued afterwards or not having lasting after-affect on each other can not be termed as dyadic communication. Thus dyadic communication is rather dyadic inter-communication. As for example we can cite the case of the dyadic communication between Jesus and Peter or between Socrates and Plato. It seems, therefore, that dyadic communication not only invoves two persons in face-to-face dialog only in outward or superficial or mechanical way, rather it brings the two persons into a sphere of inter-influences whereby each influences the other. Peter and Plato influenced Jesus and Socrates respectively by putting questions infront of them whereas the latters influenced the formers by answering to their questions.
A lasting communication of ideas between two persons for long duration of time or of any intensive duration of deeper impact may be called dyadic communication.
Dyadic communication may also be a parapsychic one in nature; and that is called synchronicity of thought between two persons coming in the same range of thoughtwave in the world; and this kind of phenomenon is called parapsychic dyadic communication.In such a field of communication, a scientist living in a remote part of the world may influence another thinker thinking in the same thoughtwave in the opposite part of the world.(Vide, Sailen Debnath,'Akashgarbha and Chetanagarbha: the Depth of the Sky and the Ocean of Consciousness' in The Meanings of Hindu Gods, Goddesses and Myths, Rupa & Co, New Delhi, 2009, ISBN 9788129114815)