Q&A: Plane vs plain

Each week here at the Australian Writers’ Centre, we dissect and discuss, contort and retort, ask and gasp at the English language and all its rules, regulations and ridiculousness. It’s a celebration of language, masquerading as a passive-aggressive whinge about words and weirdness. This week, we're keeping it plain and simple…

Q: Hi AWC, a quick one this week.

A: Sure, what have you got?

Q: Plane versus plain.

A: Okay.

Q: Don’t get me wrong – I can easily identify that a “plane” flies in the sky and that something “plain” is ordinary or even without embellishment.

A: Yes that’s true.

Q: So that must be why we call my aunt “plane Jane”…

A: Don’t you mean “plain Jane”?

Q: No, she’s a pilot.

A: Right. Okay.

Q: I’m also confident that an area of flat land is known as a “plain”.

A: That’s right, “The rain in Spain stays mainly on the plain”.

Q: Are you reading from a travel brochure?

A: No, it’s just a famous sentence from My Fair Lady to test the elocution in someone’s speaking voice.

Q: You do realise that most of the rain in Spain falls in the northern mountains though, right?

A: Let’s keep going. Another noun you’ve missed is the tool for shaving off wood one layer at a time, called a “plane”. It’s also its own verb too – you “plane the surface of the wood”.

Q: Ooooh, maybe THAT is why we call my aunt “plane Jane”. She does love that workshop of hers.

A: Could be.

Q: Alright, but now to my dilemma. If a plain is a flat area, then do we refer to being connected on “a spiritual plain”? Because I thought it was “spiritual plane”?

A: Ahhhh, yes it appears at odds with your definitions. But it should be “plane”.

Q: Why? In plain English please.

A: Because for all the nouns of “plane” – you forgot the most important one: a flat or level surface. As Macquarie Dictionary reminds us, in mathematics a plane is a surface where the straight line joins any two distinct points and lies entirely within it.

Q: Ah, well that makes more sense.

A: It’s just that people often think of “plane” – as in an “aeroplane” – first, when really they should look at where aeroplanes get their name – from the ability to plane or glide through the air.

Q: So why have we ended up with two words that both mean “flat”?

A: Good question.

Q: Thanks, it’s my job.

A: “Plain” came from the Latin “planus” and that did indeed mean flat – both physically or figuratively (as in simple, non-elaborate or easy to identify etc). But around the 1600s, along comes “plane” – derived from the same source “planus” and “planum”. It was decided that “plain” was doing too many jobs, so they gave all the physics and maths layer stuff over to “plane”. And the rest was history.

Q: Well, the rest was etymology.

A: Yes, okay.

Q: So unless you’re talking about a geographical feature that is a large flat area, everything else to do with flat is going to be “plane”?

A: Plain and simple. This includes all your physical planes, astral planes and so on.

Q: I wonder if they have business class on astral planes?

A: That joke was rather plain.

Q: It certainly fell flat.

A: Well, thanks for playin’ the plane game.

If you have a grammar gripe or punctuation puzzle that you’d like us to explore, email it to us today!