+)
Plus[a, b, ...]1 + 2
Plus performs basic simplification of terms:
a + b + a
a + a + 3 * a
a + b + 4.5 + a + b + a + 2 + 1.5 b
Apply Plus on a list to sum up its elements:
Plus @@ {2, 4, 6}
The sum of the first 1000 integers:
Plus @@ Range[1000]
Plus has default value 0:
DefaultValues[Plus]
a /. n_. + x_ :> {n, x}
The sum of 2 red circles and 3 red circles is...
2 Graphics[{Red,Disk[]}] + 3 Graphics[{Red,Disk[]}]