Following the third position; number four in a countable series.

Roget 413: melody, rhythm, measure; rhyme etc. (poetry) 597.    pitch, timbre, intonation, tone.    scale, gamut; diapason; diatonic chromatic scale^†, enharmonic scale^†; key, clef, chords.    modulation, temperament, syncope, syncopation, preparation, suspension, resolution.    staff, stave, line, space, brace; bar, rest; appoggiato^†, appoggiatura^†; acciaccatura^†.    note, musical note, notes of a scale; sharp, flat, natural; high note etc. (shrillness) 410; low note etc. 408; interval; semitone; second, third, fourth &c.; diatessaron^†.    breve, semibreve [Mus.], minim, crotchet, quaver; semiquaver, demisemiquaver, hemidemisemiquaver; sustained note, drone, burden.    tonic; key note, leading note, fundamental note; supertonic^†, mediant^†, dominant; submediant^†, subdominant^†; octave, tetrachord^†; major key, minor key, major scale, minor scale, major mode, minor mode; passage, phrase.    concord, harmony; emmeleia^†; unison, unisonance^†; chime, homophony; euphony, euphonism^†; tonality; consonance; consent; part.    [Science of harmony] harmony, harmonics; thorough-bass, fundamental-bass; counterpoint; faburden^†.    piece of music etc. 415 [Fr.]; composer, harmonist^†, contrapuntist (musician) 416.    ... show more

One of four equal parts.

synonyms: fourth part, one-fourth, one-quarter, quarter, quartern, twenty-five percent.

Roget 97: quadrisection, quadripartition^†; quartering etc. v.; fourth; quart; quarter, quartern^†; farthing^†, fourthing; quadrant.   

Dutch: kwart, vierde
Polish: ćwierć, jedna czwarta, czwarta część, 1/4, ćwiartka

The musical interval between one note and another four notes away from it.

Polish: kwarta

Coming next after the third and just before the fifth in position or time or degree or magnitude.

synonyms: 4th, quaternary.

Roget 96: fourfold, four times; quadrable^†, quadrumanous^†, quadruple, quadruplicate, quadrible^†; fourth.    quadrifoliate^†, quadrifoliolate^†, quadrigeminal^†, quadrigeminate^†, quadriplanar^†, quadriserial^†.    ... show more

Polish: czwarty

In the fourth place:
— Fourthly, you must pay the rent on the first of the month.

synonym: fourthly.