n. & adj.
n. 1 the position in a sequence corresponding to that of the number 4 in the sequence 1-4. 2 something occupying this position. 3 the fourth person etc. in a race or competition. 4 each of four equal parts of a thing; a quarter. 5 the fourth (and often highest) in a sequence of gears. 6 Mus. a an interval or chord spanning four consecutive notes in the diatonic scale (e.g. C to F). b a note separated from another by this interval.
adj. that is the fourth. fourth dimension 1 a postulated dimension additional to those determining area and volume. 2 time regarded as equivalent to linear dimensions. fourth estate joc. the press; journalism. fourthly adv.
[ OE feortha, feowertha f. Gmc ]