seventh (adj., n.)

"next in order after the sixth; an ordinal numeral; being one of seven equal parts into which a whole is regarded as divided;" c. 1300, from seven + -th (1), replacing earlier sevende, seveth, from Old English seofunda (Anglian, Northumbrian), seofoþa (West Saxon), from Proto-Germanic *sebundon (source also of Old Norse sjaundi, Old Saxon sivondo, Old High German sibunto, German siebente, siebte). The music note sense is from 1590s.

Others are reading

Definitions of seventh from WordNet
seventh (n.)
position seven in a countable series of things;
seventh (n.)
one part in seven equal parts;
Synonyms: one-seventh
seventh (n.)
the musical interval between one note and another seven notes away from it;
seventh (adj.)
coming next after the sixth and just before the eighth in position;
Synonyms: th