add /ˈæd/ verb
adds; added; adding
adds; added; adding
Learner's definition of ADD
[+ object]
: to put (something) with another thing or group of things
: to mix or combine (an ingredient) with other ingredients
: to include (something) with something else
[+ object] : to cause something to have (a usually good quality or characteristic)
: to put (two or more numbers or amounts) together to find a total or sum
[+ object]
[no object]
opposite subtract
[+ object] : to say or write (something more or extra)

add insult to injury

see 2insult

add on

[phrasal verb]
add (something) on or add on (something)
: to put (something) with another thing or group of things often + to
◊ The phrase add on to is also written as add onto.

add to

[phrasal verb]
add to (something)
: to make (something) larger, better, or greater
◊ Phrases like add to this/that and added to this/that are often used informally to introduce a statement about something that makes a thing or situation better, worse, more important, etc.

add up

[phrasal verb]
: to be added together and equal the expected or correct total usually used in negative constructions
: to make sense : to seem to be logical or true
: to slowly increase and become a large number or amount
add (something) up or add up (something) : to put together or count (the number or amount of something) to find the total
add up to (something)
: to have (a number) as a total
: to produce (a specified result)

— added