# Are "on par" and "in parity" equivalent expressions?

In an unrelated reply to one of my questions, someone used the following expression type.

x and y are on par while x and z are not

I use a similar expression (see below). However, I'm curious if they are equivalent with respect to colloquial meaning, popularity, etc. In fact, I'm a bit worried that the one I am used to is incorrect (or maybe archaic or confusing).

x and y are in parity, while...

or

x and y are of the same parity, while...

Are both ways on par with each other or are they of different parity (yes, the usage of both is intended)? In what why do they differ?

• Hi - I'm pretty confused. Is that link correct? What does 'on pair' have to do with olfaction? I can't find a reference to it. Commented Jul 31, 2015 at 9:06
• @chaslyfromUK Well, the link says that it's an unrelated post (I used it for a full example of the context). If you view the second paragraph's third line, you'll see that the first two words are "on pair" (at least on my screen). Commented Jul 31, 2015 at 9:09
• @KV - Nope. I used text search and couldn't find 'on pair'. However I have just tried again and this time I found 'on par'. I'm still confused. Commented Jul 31, 2015 at 9:36
• @chaslyfromUK Hehe, I'm confused in regard to what you're confused about. You're not confused because you didn't find the text during your first attempt, are you? If you disregard the link provided (perhaps a bad idea, although I wrote it was unrelated), the actual question is if on par and in parity (or of the same parity) are equivalent expressions. Sorry if the question wasn't ultra-cristal-clear. I do appreciate your trying to understand and clarify it. Commented Jul 31, 2015 at 9:40

"Par", from the Latin word for "equal," means having the same value as. The comparison is either of two things to each other

Your skills are on par with hers.

or with some expected or average value

I'm not feeling up to par to day.

"Parity" has two meanings. The first is synonymous with "par":

The nuclear arsenals of the US and Russia are at parity.

But "parity" can also mean taking one of two mutually exclusive states. This is mostly used in physics and mathematics:

In the reaction, two neutrinos of different parity are emitted -- one with spin up and one with spin down.

The way "on par" was used in original comment is not common in English. I interpret the author to mean "x and y mean the same thing". However, this interpretation is not common.

"Par" comes from the sport of golf, meaning "the number of strokes a first-class player should normally require for a particular hole or course." To say that x and y are both "on par" is to say that they are both have achieved the same level of excellence. If both x and y are "on par", this does not mean that "x and y mean the same thing".

Likewise, the phrase "x and y are in parity" is not very common in English. "Parity" in the ordinary sense (not engineering) means a state or condition of equality, i.e. has the same magnitude. There is some implication that x and y are governed by independent processes. To say that there is "Parity between x and y." implies that x and y have both risen (or fallen) to the same level, independently.

Notice that "parity as equality" does not imply that x and y have the same meaning, but only that they have the same value or magnitude.

• The way the author intended is that the terms need not to be of the same meaning, so you're right in your second paragraph - he only meant that they are equal in regard to a certain property (in this case, the formality/style. As for me, I use in parity with as equal to with regard/respect to a certain quality/property. And I was curious if on par and in parity were interchangeable. Commented Jul 31, 2015 at 9:48
• As an example, just to verify that we're understanding each other: if we talk about human rights, men and women are of the same parity but if we talk about gender, they're not. If two subjects are of the same parity with respect to every and any conceivable regard, they might be said to be exactly/precisely equal. Odd numbers are of the same parity when it comes to the divisibility by two. But only seven is equal to seven. In math, we call it equivalence classes. Commented Jul 31, 2015 at 9:52
• @KonradViltersten Thanks for these clarifications. My overall impression is that you may be putting too much weight on the phrases on par and in parity. I would suggest using other terms and expressions to make clear all these distinctions. I would only use "on par" when there was some clear standard that constituted "par" for that property or attribute. I would only use "in parity" when x and y were in some sort of "race" or "contest", and "in parity" meant that the race was "tied". Commented Jul 31, 2015 at 10:59
• @KonradViltersten Using your example, I would say that men and women have the same rights as humans, but in terms of relative privileges in society, they do not have parity. I would not use the phrase "...of the same parity...", because the condition of parity either exists or it does not. It makes no sense to say "...of the same parity...". Commented Jul 31, 2015 at 11:03