eighteenth       
 ordinal number uk/ˌeɪˈtiːnθ/ us/ˌeɪˈtiːnθ/
 第十八(的)
18th written as a word
  Next Monday is the eighteenth (of February). 下周一是(2月)18日 
 eighteenth      
noun [ C ] uk/ˌeɪˈtiːnθ/ us/ˌeɪˈtiːnθ/
 十八分之一
one of 18 equal parts of something