1join (something) to something else so as to increase the size, number, or amount:a new wing was added to the buildingsome box offices now add on a convenience charge (as adjective added)one vitamin tablet daily will give added protection
[no object] (add up) increase in amount, number, or degree:watch those air miles add up!
2put in (an additional element, ingredient, etc.):chlorine is added to the water to kill bacteria (as adjective added)the fruit juice contains no added sugar
contribute (an enhancing quality) to something:the suite will add a touch of class to your bedroom
3put together (two or more numbers or amounts) to calculate their total value:they added all the figures upadd the two numbers together
[no object] (add up to) amount to:this adds up to a total of 400 calories figurativethese isolated incidents don’t add up to a true picture of the situation
[no object, usually with negative] (add up) informal seem reasonable or consistent; make sense:many things in her story didn’t add up
4 [reporting verb] say as a further remark: [with direct speech]:‘I hope we haven’t been too much trouble,’ she added politely [with object]:we would like to add our congratulations
late Middle English: from Latin addere, from ad- 'to' + the base of dare 'put'