When I have a directed relation I call one of the items taking part a subject and other an object. Is there a corresponding term for a bidirectional relation? I know I can call both items a relation objects, but I would like some other term to distinguish from directed relation.

  • What is a "directed relation"?
    – Robusto
    Aug 18, 2015 at 12:32
  • When you have a relation hasChild, it is directed and subject is a parent and object is a child. Example of an undirected relation would be for example knows, because when you know somebody he/she also knows you. Aug 18, 2015 at 12:36
  • Knows sounds rather bidirectional then, I think.
    – oerkelens
    Aug 18, 2015 at 12:37
  • I copied this from directed and undirected graphs. But I agree bidrectional is more understandable. I corrected the question. Aug 18, 2015 at 12:40
  • I'd tend to put on my programming hat and say "unidirectional" and "bidirectional". Though one might also use "association" to refer to a linkage whose direction is not defined.
    – Hot Licks
    Aug 18, 2015 at 13:22

2 Answers 2


participants [Source: ODO]

Examples of usage:

  • 'a situation with two participants between which a bidirectional relation holds'

Source: Reciprocity in English: historical development and synchronic structure. Haas, F Routledge, 2010

  • 'It is a bidirectional relation denoting that two participants are socially connected and it corresponds to the generic relation offered by existing social networks.'

Source: Enterprise, business-process and information systems modeling. [LNBIP 175] Springer, 2014


Reflexives appear to be one form of bidirectional object:

"He injured himself."
"He perjured himself." (ref. Wiktionary)

And Reciprocal (Merriam Webster) describes another situation:

—used to describe a relationship in which two people or groups agree to do something similar for each other, to allow each other to have the same rights, etc.

hence: Reciprocal Pronouns: (englishclub.com)

"each other," "one another"

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