Seventeenth/ˌsevnˈtiːnθ/ Definition 1 of 2Pro Tip 1/3Ordinal Use Used to describe the order in a sequence; helpful in dates and positions. Her birthday falls on the seventeenth of April. Pro Tip 2/3Historical Periods Commonly used to refer to centuries and historical time frames. I'm studying the political changes of the seventeenth century. Pro Tip 3/3Fixed Phrases Often appears in set expressions or collocations without variation. The race ended and she finished in seventeenth place.