Sentence:  Horse <WSD>number</WSD> 5 won the race. 
Meaning of the word marked with <WSD> tags:  Indicating the position of something in a list or sequence. Abbreviations: "No" or "No.", "no" or "no." (in each case, sometimes written with a superscript "o", like Nº or &#x2116;). The symbol "#" is also used in this manner.