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Latin Grammar I, Lesson 23. Nouns Irregular in Number

In the previous lesson, we introduced the study of irregular nouns in Latin. It would not be a good use of time to study irregular nouns in a systematic way as we do regular nouns. Our goal is to simply become aware of irregular nouns so that when you see them, you are not confused. In this lesson, we will study irregular nouns which are deficient in number.

To complete the objectives of this lesson, complete the following tasks:

  1. Study the lesson for mastery.
  2. Complete the lesson assessment.

The content of this lesson is taken from chapter 23 of Alvarez’s Latin Grammar.


l. Quaedam singulari numero tantum declinantur, ut nemo, pontus, lutum; et pleraque eorum, quae metimur aut ponderamus, ut triticum, oleum, aurum, ferrum.

Translation: Certain (nouns) in the singular number only are declined, as: nemo (no one), pontus (sea), lutum (mud); and most of those which we measure or weight, as: triticum (wheat), oleum (oil), aurum (gold), ferrum (iron).

Some of these nouns are irregular in form, but not in the ideas they signify. For example, the Latin noun nemo means “no one”. It’s obviously that the idea signified by this noun would never need to be expressed in the plural number. The same is true of the other examples given. The second group are nouns that name materials or kinds of matter. We never refer to such ideas in the plural, so there are no names for these. Therefore, the irregularity of these nouns is a matter of common sense: there are no ideas to express with plural names.

II. Quaedam plurali solum, ut cani, canorum, penates, penatium, castra, calendae.

Translation: Certain (nouns) are declined in the plural number only, as: cani, canorum (grey hairs); penates, penatium (household gods); castra (tents), calendae (calends).

As with the singular nouns above, these “irregular” nouns are not irregular when we consider that the ideas they signify have no singular expression. For example, cani refers to the grey hairs of an old man’s head, and would not be used in a singular form to refer to a single hair. Likewise, the Latin word castra is plural and is used to name a military camp by referring to it as a collection of tents (castra).


This lesson simply introduces us to irregular nouns that lack either plural or singular forms, based on the ideas they signify. There are many more, so be on the lookout for them in your Latin reading lessons.

If you’d like to dig deeper into irregular nouns, study the chapter on Heteroclite nouns in Lily’s Latin Grammar.

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