Acronym of personal identification number.

(organic chemistry) Initialism of preferred IUPAC name.

(music) Any two or more pitches or pitch classes all of which occur simultaneously, or at the same time. It may be thought of as a more general term for any possible chord. Any chord progression or harmonic progression is then a simultaneity succession, though not all simultaneity successions are harmonic progressions and not all simultaneities are chords.

(music) An equivalence class of all pitches that are octaves apart, and which would be labeled by an integer, not a traditional letter name.

(uncountable) A feeling of sympathy at the misfortune or suffering of someone or something. / (countable) Something regrettable. / (obsolete) Piety.

(transitive) To feel pity for (someone or something). / (transitive, now regional) To make (someone) feel pity; to provoke the sympathy or compassion of.

Short form of what a pity.

(music) To be played very softly.

A dynamic sign indicating that a portion of music should be played pianissimo. / A portion of music that is played very softly.

(linguistics, anthropology, etc.) Initialism of Proto-Indo-European.