Can somebody please point me in the correct direction so that I can understand why the following declension is done that way?

The neutral noun "caput" came up in a correspondence course I am taking, and I attempted unsuccessfully to decline it using the rules in Lucien Sausy's "Grammaire latine complète", as well as in the declination rules shown in the Collins dictionary. Finally, latin.cactus2000.de showed me that it is in the 3rd declension, and shows it in N-V-Ac-G-D-Ab form: SINGULAR: caput, caput, caput, capitis, capiti, capite; PLURAL: capita, capita, capita, capitum, capitibus, capitibus

In particular, what makes it decline that way in N-V-Ac singular?

Thank you!

  • When declining nouns, different traditions of teaching Latin order the cases differently for different reasons. Ordering them as N-V-Ac-G-D-Ab highlights the similarities between N-V-Ac (particularly for neuter nouns and plurals) and helps with memorization and reciting the declensions. Other traditions would consider that this order places too much emphasis on the nominative form, leading to later confusion about the other forms. That is what has happened in your case, as is explained in the answers below, which are informed by a more linguistic tradition. Jan 27, 2022 at 18:00

2 Answers 2


Contrary to what one may expect, the nominative form is not the starting point for declension - the stem is. A large number of 3d declension nominals is characterised by having two distinct stems - a nominative singular and an oblique one.

The nominative singular stem in such cases is basically irregular, not necessarily further segmentable, and the only other forms it figures in are those that always = the nominative (neuter accusative, vocative). Examples include mēns, pollex, tempus, alacer "mind, thumb, time, lively". All of the actual case endings attach to the oblique stem, which for these words is ment-, pollic-, tempor-, alacr-.

With some knowledge of historical/synchronic phonology, one will notice that the two stems are often more or less transparently related; most commonly the oblique stem exhibits a reduction to /i/ of the stem-final short vowel in an open syllable - this is also what's happened here. That vowel is most commonly /e/, and caput is peculiar in being the only noun that ends in /ut/, but the reduction is still expected. A following /r/ blocks the reduction. It's not too difficult to formulate phonological rules converting the oblique stem into the nominative one, or better, deriving both from a common underlying form.


There are two ways to approach this question that I would like to distinguish:

  • Historical. In the historical version the question would be: "Where does the form caput come from and why is it different from what I see in the other cases?"
  • Practical. In the practical approach the question would be: "How do I actually figure out what each case of caput looks like?"

For a starting student I warmly recommend focusing on the practical side of things, and only getting the historical background later if you are interested. I think historical matters are easier to study when you have sufficient practical experience, so starting practical might be best even if your end goal is historical.

For the practical point of view I will point you to this question and its answer: Why do we learn the genitive singular of each Latin noun? The conclusion is that in order to find all the forms of a Latin noun, such as caput, you need three pieces of information: singular nominative form, singular genitive form, and the gender. Therefore what you need to know is not "caput" but "caput, capitis, neuter". You get most forms from the genitive. To be able to find the forms, there need not be any sense in the connection between caput and capit-; you just need to know that these two elements together make up the word (together with gender information), not either of them alone.

In this particular case: Because caput is neuter, the singular accusative and vocative is the same as the nominative. All other forms you get by adding endings to the stem capit- you get by stripping the genitive ending from the genitive. My recommendation at first is to simply learn that this is so; Latin declension is fairly regular and there are not too many kinds of words.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.