plus sign vs pro

plus sign

noun
  • The symbol + used to denote the operation of addition, to indicate that a number is positive, and so on. 

pro

noun
  • An advantage of something, especially when contrasted with its disadvantages (cons). 

  • Professional. 

  • A prostitute. 

  • A professional sportsman. 

  • A chemical prophylaxis taken after sex to avoid contracting venereal disease. 

  • A person who supports a concept or principle. 

prep
  • In favor of. 

adj
  • Professional. 

How often have the words plus sign and pro occurred in a corpus of books? (source: Google Ngram Viewer )