What part of speech are "plus", "times", and "minus"

In mathematics one will often say "This plus that" or "This times that". This means "This added too that" and "This multiplied by that".

Multiply, Add, Subtract, Divide - All are verbs. But what part of speech is "times" or "plus". It's wrong to say "times this by that" or "plus this with that". So they do not seem to be verbs, but they imply an action.

Solution 1:

M-W defines plus (definition 3, used in addition) as a preposition.

This would make sense if you think of "Three plus four" as "Three added to four."

Alternatively, you could hedge your bets and call the operator a conjunction, which would make sense if you think of "Three plus four" as "Three and four."

Solution 2:

If I say 'Jelly with ice-cream is nice', it seems to follow the same structure as 'One plus two equals three'.

So in the sentence 'One plus two equals three', 'One plus two' I would have said was a subject clause, 'equals' is the verb, and 'three' is the predicate.

Therefore in the context 'plus' seems to me to be a preposition, equivalent to 'with' in 'jelly with ice-cream'.