Belong to a multiple system: multiple

The parameter multiple takes the value M if the object belongs to a multiple system. For example, a galaxy belonging to a pair of galaxies have multiple=M.
Presently multiple accounts for the association in projection on the sky and therefore does not reflect for sure a physical association: members of "false" pairs will have multiple=M.

Often, un-resolved systems, as for example closely interacting systems of galaxies or faint galaxies which have simply not been entered separately in the database have both objtype=M and multiple=M.
The simple membership to a cluster of galaxies does not imply a galaxy to carry multiple=M. M is used for member of pairs or small and close multiplets. We do not exclude that in the future this flag will be extended to code G or C respectively for members of pairs and clusters, we may also like to distinguish averred physical pairs, discordant pairs or possible pairs.

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