Definition of "affinity" []

• A natural attraction, liking, or feeling of kinship. (noun)
• Relationship by marriage. (noun)
• An inherent similarity between persons or things. See Synonyms at likeness. (noun)
• Biology A relationship or resemblance in structure between species that suggests a common origin. (noun)
• Immunology The attraction between an antigen and an antibody. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "How could two chemists converse on chemistry without the use of the term affinity, and the theoretical conception it involves?"
• "Yes; but the term affinity is objectionable in this case, because, as that word is used to express a chemical attraction (which can be destroyed only by decomposition), it cannot be applicable to the slight and transient union that takes place between free caloric and the bodies through which it passes; an union which is so weak, that it constantly yields to the tendency which caloric has to an equilibrium."
• "This is the premier action that has a level of coordination, but they are what you call affinity groups that are going to be doing these spontaneous actions all across the city that we don't even know about, so we will try to capture them as they happen and bring them back to you as we can."