tenth / ten[unvoicedth]/ • n. constituting number ten in a sequence; 10th: the tenth century | the tenth of September the tenth-floor locker room. ∎ (a tenth/one tenth) each of ten equal parts into which something is or may be divided: a tenth of a second. ∎ the tenth grade of a school. ∎ Mus. an interval or chord spanning an octave and a third in the diatonic scale, or a note separated from another by this interval.DERIVATIVES: tenth·ly adv.