Cases of word usage

1) a water animal with a hinged double shell e.g. and oyster, a mussel (bivalve)

2) (of a word) having a double or doubtful meaning (equivocal)

3) a curve of two equal parts formed by cutting through both bases of a double cone (hyperbola)

4) an interval of eight notes between two notes so that the first has a pitch double the value of the other; the first eight lines of a sonnet; verse of eight lines (octave)

5) a kind of shellfish with a hinged double shell, eaten as food (scallop)