# Commas to separate a dependent clause or not?

I'm writing about a player playing a game and probabilities. I tried to cut down the sentence, so don't concentrate too much on the sense rather than the commas.

Would you write my sentence like this

The player should accept if the probability that this is indeed the best item is bigger than some other probability.

or with commas like this

The player should accept if the probability, that this is indeed the best item, is bigger than some other probability.

• If there's any comma in this sentence, it should be after accept, since that's where an optional comma dip might occur in speech. Note that this is immediately before a subordinate clause (though not the one mentioned in the question). Commented Jun 6, 2014 at 16:17

The commas are wrong and indeed make no sense unless you just mentioned the first probability in the previous sentence. In which case you should just throw out the clause altogether, what with your goal to cut down the sentence and all.

So in short, iff that clause is a parenthetical, then you can offset it with commas as such. And the clause is a parenthetical iff the rest of the sentence works without it.

P.S.: what should the player accept? It's missing from the sentence. You probably mean "accept it" rather than just "accept". Or better still, "the player should accept that the probability X can be bigger than probability Y".

• @RegDwight re your P.S, it makes sense as written if you assume that the previous sentence establishes that the player has a choice between accepting an item or not.
– Rupe
Commented Jun 6, 2014 at 15:26
• @Rupe right. Good point. Commented Jun 6, 2014 at 15:29
• Context might also make sense of the "other probability" at the end. And unless it is discussed/defined as a probability of some (other) condition holding, it'd be better just to say something like "bigger than some threshold".
– Rupe
Commented Jun 6, 2014 at 16:00
• I tried to cut down the sentence to make it less technical (that's why just "accept" and "other probability"). The player is given items, one after another, and on each of those occasions ha to decide whether to take that currently presented item, or to discard it (then he's presented the next one). Commented Jun 7, 2014 at 7:57

You may use dash (super-comma) to set off "extra information"

The player should accept if the probability -that this is indeed the best item- is bigger than some other probability.