1. (n.) The tonic or first tone of the scale in which a piece or passage is written; the fundamental tone of the chord, to which all the modulations of the piece are referred; -- called also key tone.

2. (n.) The fundamental fact or idea; that which gives the key; as, the keynote of a policy or a sermon.

aroma attribute badge banner be characteristic brand cachet cast character characteristic characterize configuration cut define demarcate describe device differentia differential differentiate distinctive feature distinguish dominant earmark feature figure flavor gust hallmark idiocrasy idiosyncrasy image impress impression index indicant indicator individualism insignia key key signature lineaments major major key mannerism mark mark off mark out marking measure mediant minor mold nature note odor particularity peculiarity pedal point picture property quality quirk representation representative savor seal set apart set the pace set the tone shape sigil sign signal signature singularity smack sound the keynote specialty stamp subdominant submediant subtonic supertonic sure sign symptom taint tang taste telltale sign token tonality tonic tonic key trait trick