New to this particular community.

My question relates to the word propaedeutic. In particular, I have witnessed the "a" interwoven with "e" to produce propædeutic. I once read that this is an example of a diphthong. Is the æ glyph simply used to denote a difference in pronunciation? Could anyone shed light on the roots of this linguistic practice?

And, if I may, why is propaedeutic, or propedeutic more generally, not recognized as a word when written out in this context?

Any insight?


3 Answers 3


Those are called ligatures, when two letters are tied together in a special way.

The older custom of doing so in typeset Modern English text for certain combinations of A+E or O+E no longer holds, so you should today just leave them separated except when citing an older passage verbatim.

In this answer that now resides on one of our sister sites, I previously wrote:

If push comes to shove, a reasonable general rule is:

  • Use explicit lexical ligatures only for the things that make sense in the language you’re writing in, such as Æ, æ in Icelandic or Old English and Œ, œ in French.
  • Leave the selection of typographic ligatures to the software, which should happen automatically for those situations where it would not look right without them.

Our word ligature comes from the Latin first declension noun ligātūra, which was in turn derived from the Latin verb ligāre meaning to bind. It’s a tie.

As for why something is “not recognized as a word” when written with a ligature, that’s a defect of whatever spellchecking software you’re being subjected to.

  • This is a duplicate. The fact that it was wrongly closed (the other question involved specifies 'in typesetting', unlike this one) notwithstanding. I trust I CV-d at the closed thread for POB reasons. Dec 3, 2019 at 19:17
  • 1
    @EdwinAshworth Got it, thanks.
    – tchrist
    Dec 3, 2019 at 19:40
  • Thank you. I apologize for duplicate inquiries. By the way, propaedeutic is not recognized as a word on this forum with—or without—a ligature.
    – Tom
    Dec 3, 2019 at 22:18
  • @Tom That “not recognized” thing is a function of your web browser, not of this site. Certainly the OED recognizes it (behind its paywall), which is enough for most of us. :) A subject or course of study which forms an introduction to or preparation for an art or science, or to more advanced study.
    – tchrist
    Dec 3, 2019 at 22:45
  • @tchrist I see. I got caught in the weeds with that one. Also, once a question is dubbed a duplicate, is it eventually deleted? Can I mark my question as answered here?
    – Tom
    Dec 3, 2019 at 23:21

In English, the ae ligature (Æ/æ) is simply a typographic variant of ae, and generally does not signal anything different about pronunciation vs. the separate letters; in American usage, words that use ae (or, historically, æ) are often (but not always) respelled to use e instead of ae. See Wikipedia on Æ.


Usage changes with time, starting with Latin diphthongs. Œconomics -> Oeconomics -> Economics. Generally, the US is further along in this transformation than the UK.

Of course there are other ligatures for common combinations (like fi fl etc.) which have nothing to do with Latin diphthongs. Here is a picture from Wikipedia:
fi fl

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