attention has 4 distinct synonyms spread across 2 of its 6 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is inattention.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the process whereby a person concentrates on some features of the environment to the (relative) exclusion of others
Synonyms, antonyms and the broader and narrower relations for attention come from Princeton University’s WordNet. Full sources and licences.
the work of providing treatment for or attending to someone or something
“no medical care was required”
a general interest that leads people to want to know more
“She was the center of attention”
a courteous act indicating affection
“she tried to win his heart with her many attentions”
the faculty or power of mental concentration
“keeping track of all the details requires your complete attention”
a motionless erect stance with arms at the sides and feet together; assumed by military personnel during drill or review
“the troops stood at attention”