What is the meaning of plus?

noun

• A useful or valuable quality.
  • synonyms: asset
• The arithmetic operation of summing; calculating the sum of two or more numbers.
  • usage: "the summation of four and three gives seven"; "four plus three equals seven"
  • synonyms: summation, addition

adjective

• On the positive side or higher end of a scale.
  • usage: "a plus value"; "temperature of plus 5 degrees"; "a grade of C plus"
• Involving advantage or good.
  • usage: "a plus (or positive) factor"
  • synonyms: positive