What is the difference between text alignment, text justification, and quadding?

Question

I'm a German software developer who needs to add a parameter to a function that lets users choose if the created text "sticks" to the left, to the right, or is (horizontally) centered. For this concept I have found three expressions: (1) text justification (2) text alignment (3) quadding.

Is there any difference between the three choices in how they are used / what they mean?

Text alignment

From writing HTML, I know text alignment, e.g. mozilla docs.

It's also called "align" in Google Docs and Libre Office Writer:

Text justification

The same concept is called "text justification" in the PDF specification.

Quadding

I have only ever seen this in the PDF specification. There it is used as a synonym for "text justification".

The best explanation what this means comes from http://www.happydragonspress.co.uk/tips/beginners/justification.shtml :

Em spaces are sometimes grouped in with Quads. Quads (or Quadrats) are like extra wide spaces, in multiples of 1 Em: 2 Em, 3 Em, 4 Em and occasionally 5 Em. These extra wide spaces are particularly useful for centering things and, above all, for poetry.

So quads are a tool to implement centering.

Other occurences:

• https://docs.apryse.com/api/dotnetcore/api/pdftron.PDF.Field.TextJustification.html

Google N-Gram

Looking at Google NGrams, text alignment seems to be by far the most common one:

Justification vs Alignment

According to https://yesimadesigner.com/justification-vs-alignment/ and https://www.shutterstock.com/blog/justify-vs-align-guide-to-type-alignment

• Uses "justified" as one type of text alignment. It's called "justified" in Google Docs / Writer as well.
• Maybe even more precise would be that text is either justified or aligned. If it is aligned, it can be left/center/right aligned.

Answer 1

These undoubtedly have proper meanings that typesetter would know about.

But 99% of English speakers are not typesetters, and we only get a vague idea from the use of these words in word processing applications, or perhaps from writing HTML and CSS.

Alignment is how the rows of text line up: Do they line up to the left, leaving the right part ragged, or to the right, leaving the left ragged. Or the alignment might be at the centre, leaving both left and right ragged.

I suppose you could align in other ways, for example making the first letter of the second word of each row of text line-up, or making a pattern (as in Lewis Carroll's "Mouse's tale")

Justification is about making both left and right edges line up straight, usually by inserting extra space between the words. And also people use "justification" to talk about not justifying the text but leaving it ragged - so justification comes to mean the same as alignment... _{and the real typesetters start to seethe at how muggles like me are using their words wrongly.}

Quadding is a technical term that isn't used by non-specialists.

You are just talking about how the text lines up, so use "alignment". if it is user-facing text.

Answer 2

Alignment is the simplest. It takes one vertical line & makes everything either start, end or centre on it. It does nothing else, so the opposite end of each line is free to finish where it needs, without shrinking or stretching and optionally without hyphenation.
This is how anything written on a mechanical typewriter will look*, each line just has to end before you run out of space, no other adjustment is made. Because left & right alignment are simple 'start from one end' processes, this is as easy to do in physical typesetting with boxes of lead letters as it is for a computer. No 'math' needed. Centre alignment needs measurement, which makes it still simple enough for a computer, but a typesetter would be getting their calculator/slide rule out. Each line is still 'just as long as it needs to be', with the word count adjusted to fit.

To go into Justification, you need two more 'tech words' - Kerning and Tracking.
From Wikipedia -

In typography, kerning is the process of adjusting the spacing between characters in a proportional font, usually to achieve a visually pleasing result. Kerning adjusts the space between individual letterforms, while tracking adjusts spacing uniformly over a range of characters.

Now, as simple as this may sound, kerning is as much art as it is craft. The default gap between letters must be worked out for every potential letter pair. There are some highly complex rules to get the artist/foundry started, but ultimately it comes down to their judgement. A finished font can have between 200 & 1,000 of these dedicated individual pairs mapped.

So, now we come at last to Justification. In it's simplest form, 'fully justified' means that both left & right sides form a perfect vertical line. 'Perfect' however is already subject to human optical perception. Does a letter start from the first vertical, does it start from the beginning of the serif? What about if the line starts with an 'O' which has neither vertical nor serif?
Once that has been decided, then the typesetter/computer must figure out how much extra space to include where necessary to keep the overall look, whilst hitting both edges precisely and not leaving big gaps or crushing letters together.

This is hard.
Dedicated page layout applications such as Quark Express can do it beautifully, time after time. Word processors & such as email apps generally make an ugly mess of it - they tend to prefer to adjust tracking, without keeping an 'eye' on the visual impact kerning is capable of. Sometimes they seem to adjust kerning too… & make an awful salad of it. I have never been able to figure out just how they manage to get it so badly wrong. This is why you should never do pre-press in Word. Any real typesetter will just cry.

I have never used quadding. I've always trusted Quark [or these days often Pages, which is really pretty good at it] to be able to get it right and have never needed [nor probably have the skill] to manually adjust this myself.

^{I hope this is comprehensible. To simplify it this far I have left huge swathes of technical knowledge and terms out entirely. This is not the full story of how it's done, but I think is potted far enough to not have people nod off halfway through ;)}

*OK, so a mechanical typewriter uses a mono-spaced font, but otherwise this is easy to visualise for demonstration purposes.

Answer 3

Alignment in this context means whether the lines of text are on the left side of the page, the right, or centered. It’s also common to speak of a “political alignment” on the left, right or center.

Justification in this context means making every line of text (except possibly very short ones at the bottom of paragraphs) the exact same width. This is usually done by expanding the space between words and hyphenating in appropriate places, but sometimes by stretching the font slightly wider. In theory, you could have many variations on this (for instance, many German publishers historically let punctuation protrude into the right margins), but in practice, only one is ever used in English. Modern word processors display it as an alternative to the three “align” commands, as in your screenshot.

A quad is an amount of horizontal space, which varies from document to document. It’s often used for indentation and to increase the left and right margins.

Answer 4

"Text alignment" and "text justification" are synonymous, it just depends on where it is being used as you have already discovered - Word / Google docs / Writer as opposed to the PDF specification. The result is the same.

"Quadding" is slightly different but achieves a similar result. It comes from the days of hand type setting with individual letters. Spaces between words were created by inserting blank pieces of type. If there was a lot of space to take up, say there was only one or two words on the line, then extra wide spaces were inserted as each line of set type had to be the same length. This was known as "quadding" and could be left, right or in the middle of a line. There is a brief definition of the word as a verb in Merriam Webster, and a longer description on the PrintWiki site which says that, "with the advent of desktop publishing, the term quad is being used less and less often".

Answer 5

To answer the specific question here (others have done varying jobs with the generalities, and votes reflect that):

add a parameter to a function that lets users choose if the created text "sticks" to the left, to the right, or is (horizontally) centered. For this concept I have found three expressions: (1) text justification (2) text alignment (3) quadding.

I would recommend that you use the term alignment for this choice. We say that objects are "aligned" if a specific part of each one lies on a shared straight line.

Text is

• left-aligned if the left side of each line is at the left-hand side of the page (less margins)
• right-aligned if the rightmost end of each line is at the right-hand side of the page
• centre-aligned (aka centred) if the middle of each line is midway between the sides.

When dealing with languages that are written with right-to-left scripts, we may need to use direction-dependent terms - start-aligned and end-aligned - if we want the alignment to be correct for the writing direction.

Answer 6

Your image shows a menu with four options.

• "Text alignment" is whichever option is selected.
• "Text justification" is specifically the fourth option.
• "Quadding" is some technical term that the user doesn't need to worry about.