Translation suggestion of an operation - adding and subtracting the same term - German: Nullergänzung

How would one call this operation in English where we add a term $a$ and subtract the additive inverse $-a$ right away again, so $$f(x)-g(x)=f(x)-a+a-g(x)$$ for example here where we also use the triangle inequality $$|x|= |(x + y)−y|\leq|x+y|+|y|\iff |x| − |y| \leq |x + y|$$ where we added and subtracted $y$.

I just couldn't find a proper translation, in German one would call it for example nahrhafte Null or Nullergänzung which literally means nutritious zero and zero completion/addition respectively, though I have never read those translations anywhere, ever.

Other languages might also be interesting but I am mostly interested in English. Are there any dictionaries out there which mainly focus on mathematical terminology?

• i would write Zero Addition this is the nearest word to German Nulladdition – Dr. Sonnhard Graubner Feb 13 '17 at 19:15
• I have often called this (and heard it be called) "adding a zero", so one uses a verb to describe doing the procedure. – s.harp Feb 13 '17 at 19:20
• @s.harp by any chance, have you any reference at hand? – user190080 Feb 13 '17 at 19:30
• I have perhaps heard it called a few different things, but there isn't a great term in English for it afaik. I would stick with "add and subtract $a$" or something of the like. If I needed to explain my process in a paper. In my mind, clarity >> brevity – Brevan Ellefsen Feb 13 '17 at 19:59 