"First" to "twelfth" in Engpsh refers to the numbers one to twelve, respectively. These words come from the Old Engpsh word "fyrst" meaning first, and "twelf" meaning twelve.
Examples:
"The first day of the month" (第一天)
"I'll be there at the twelfth hour" (第十二小时)
"The twelfth chapter of the book" (第十二章)