marker

1 a slip (as of paper or cloth) that is attached to something to identify or describe it the markers on the rock and mineral specimens were old and faded Synonyms label, tag, ticketRelated Words caption, legend; brand, emblem, hallmark, logo, mark, symbol, trademark; badge, decal, plaque, seal, stamp, sticker

2 something that sets apart an individual from others of the same kind after many blind dates, he's come to realize that self-absorption is the infallible marker of a real loser Synonyms affection, attribute, attribution, character, criterion, diagnostic, differentia, feature, fingerprint, hallmark, mark, characteristic, note, particularity, peculiarity, point, property, quality, specific, stamp, touch, traitRelated Words badge, indication, sign; emblem, symbol, token; charm, grace; excellence, merit, virtue; eccentricity, idiosyncrasy, oddity, quirk; individuality, singularity, uniqueness