O with line through it: Here's what Ø means + Examples (2024)

Have you ever seen this symbol before Ø? The Eagle eyed among you might have noticed this symbol is not English. But today, we’ll look at what it means, and when it might be helpful for you to know.

What does O with line through it mean?

O with line through it (Ø) has 4 meanings.

1. In Norwegian, Danish, or Faroese., Ø has a similar meaning to OE.

2. The symbol for diameter.

3. Empty or null.

O with line through it in the Nordics

The first example of what Ø means is its a letter in some Nordic languages. Norwegian, Danish, or Faroese.

When you see Ø, be careful not to get it mixed up with “O”. Because Ø means OE, and cannot be swapped for an “O”. In many European languages, they have the same alphabet that we do, but a few more letters dropped in there.

In other languages, Ø might be written as œ.

12 words in Nordic languages that use O with line through it

Desert Road in Danish

Beers in Danish

Deceased in Danish

Ruined in Norwegian

Trout in Norwegian

Head in Faroese

Hoof in Faroese

Buoy in Danish

Beer good in Norwegian

Cause in Faroese

O with line through it meaning diameter

But, back in English, or more like Mathematics, the symbol Ø can also be used when measuring the diameter of something.

For those who haven’t sat in a Maths classroom for some years, a diameter is a measurement taken from a shape. It’s the distance from one end of a shape to the other, and it must pass through the center of that shape.

In a circle, half of the diameter is known as the radius.

Often, people wouldn’t write the word “Diameter” because it’s too long, or “D” because that could stand for anything. Therefore, using a Ø helps people know what that number is without making it too complex.

3 examples of Ø as diameter

“It has to be Ø14 mm or more, but it can’t be more than 19 mm”

“Usual sizes for these tubes are an inner Ø1-3 nm and an outer Ø of around 10 nm.”

“A cat with intestines which are Ø8 mm and a throat Ø10 mm would likely receive a 10 mm diameter tube”

O with line through it meaning “Empty” or “None”

Staying on the topic of Mathematics, another use for Ø is a zero. The trouble with “0” is it looks like “O”. Particularly if it’s written out by hand.

Therefore, having a Ø instead means there is no confusion. It is not an “O”, it is a zero. This kind of zero might be used when it’s important to know there is nothing there, for example, when talking about banking.

It might also be beneficial when you have to use “O” and “0” in the same sentence.

3 examples of Ø as empty or none

“Your total account balance is Ø. Please add money or the account will be shut down”.

“Hey Mark, how many guests have you booked?”


“How many new toys do we have in stock?”


O with line through it in Greek

And the final meaning of Ø isn’t a meaning at all. Rather, it’s a misunderstanding. In the Greek alphabet, they have Phi (ϕ) and Theta (θ).

As you probably already noticed, with Phi, the difference is the circle is smaller and the liner goes vertically. And with Theta, it looks more like a 0 than an O. Also, the line is horizontal and stays within the 0.

Today, both Phi and Theta are used in various disciplines to show function, phase, or angle.

Of course, because our handwriting isn’t always as good as a computer’s typing, it’s too easy to write both Phi and Theta as Ø.

10 examples of ϕ and θ

Φιλοξενία (fi-lox-en-ee-ya)
To show love to strangers

ϕιλότιμο (fi-lo-tee-mo)

κέϕι (ke-fee)
Uncontainable joy

Σωϕροσύνη (sof-ros-i-nee)
Healthy in both mind and body

Θɪŋ (Thee-Ten)

Θɹi (Thee-Tie)

Nɔɹθ (In-Thee-ta)

Saʊθ (Sa-Thee-Ta)


Bɹɛθ (bre-theeta)


Hopefully now you have a better idea of what Ø means. Unlike many other symbols we’ve spoken about today, Ø has several meanings. And the meaning of Ø changes depending on what topic you’re talking about, and what language you’re talking in.

To know which usage of Ø any writer means, you simply need to use a little bit of common sense. Thankfully, this article should have given you all the tools you need to figure it out.

O with line through it: Here's what Ø means + Examples (1)

Martin Lassen

Martin holds a Master’s degree in Finance and International Business. He has six years of experience in professional communication with clients, executives, and colleagues. Furthermore, he has teaching experience from Aarhus University. Martin has been featured as an expert in communication and teaching on Forbes and Shopify. Read more about Martin here.

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O with line through it: Here's what Ø means + Examples (2024)


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