§26. Latin Adjectives: 1st and 2nd Declension Type

The basic Latin adjective that meant “big” or “great” was a word with the base magn-; the ending that followed this base depended on a variety of factors, including the gender of the noun to which the adjective was linked. A “big page” was a Magna Charta; a man known as “Charles the Great”—we call him Charlemagne—had the Latin name of Carolus Magnus; a “big work” (the main achievement of one’s life, perhaps) can be described in Latin as a magnum opus. These are the three genders of the standard Latin adjective: magnus (m.), magna, (f.), and magnum (n.). If it modifies a feminine noun, an adjective of this type will use first-declension endings; for example, when the adjective firmus, firma, firmum is combined with the feminine noun terra, it creates the phrase terra firma (“firm earth”). If attached to a masculine or neuter noun, an adjective of this type will use second-declension endings, as seen in the examples Carolus Magnus and magnum opus above.[1] For obvious reasons, then, this very common type is described as an adjective of the first and second declensions, or a 1ST AND 2ND DECLENSION ADJECTIVE.

For the purposes of this course, we seldom have to worry about questions of Latin gender; and we can blissfully ignore all problems of adjective-noun agreement, a topic that creates some anguish for students of Latin grammar. It will be enough for us to know that most Latin adjectives belong to the same class as magnus, magna, magnum and firmus, firma, firmum. For the sake of brevity, we shall usually refer to words of this type simply as magnus or firmus, assuming the existence of feminine and neuter forms to match the masculine. IF A LATIN ADJECTIVE IS LISTED WITH THE ENDING –us, YOU CAN BE CERTAIN THAT IT BELONGS TO THE 1ST ADN 2ND DECLENSION TYPE. As you would expect from the parallel nouns that we studied in chapter 2, the base of these adjectives can be determined by removing the –us ending.

It is often possible to guess the meaning of a Latin adjective from obvious English clues. We have already met firmus (“firm,” “steadfast”), whose base provides the synonymous English derivative. The same principle applies to Latin adjectives like justus, vastus, solidus, timidus, validus, and rotundus. In meaning, these words may not exactly match their English derivatives, but the differences aren’t worth worrying about. Occasionally, however, semantic changes have occurred—the Latin word crispus, for example, meant “curly-haired.” If you know that Latin curtus meant “clipped” or “shortened,” you may have a better feeling for the connotations of the English word curt. Once in a while, appearances can be deceiving: Latin longus is not the origin of English long, which is a cognate word of Germanic descent.

aequus even, equal multus much, many
bonus good pius dutiful, good
justus upright, just planus level, flat
longus long sanus healthy, sound
magnus big, great solus alone, only, sole
malus bad, evil vacuus empty
medius middle verus true

For hundreds of years, students of Latin have been learning 1st and 2nd declension adjective forms from the model of bonus, bona, bonum (bonusaum), one of the commonest words in Latin. It is the origin of the corresponding adjective in the Romance Languages—French bon, Italian buono, and Spanish bueno. Its main derivatives in English, however, are two nouns—bonus and boon. It is not uncommon for adjectives to evolve into nouns in this fashion. In English, as in Latin, we can refer to “the good” as an abstract concept; the Latin phrase summum bonum (“the highest good”) is sometimes used in English. Similarly, we can talk about a “happy medium,” using another Latin adjective as a noun. A medium may also be a physical substance “in the middle,” or a means of mass communication (plural, media), or a spiritualist who attempts contact with the dead. A magnum can be a large (two-quart) bottle—probably of champagne. Another example of the evolution of neuter adjective into noun can be seen in vacuum, an “empty space.”[2] This same Latin adjective has given us the English adjective vacuous.

You will surely spot the connection between aequus and English equal, equity, etc. Don’t be puzzled by the change in spelling: it is a regular development for the Latin diphthong ae to evolve into English e. Problems can arise, however, when this change blurs the contrast between two distinct Latin words. In English spelling terms, there is no difference between the Latin adjective aequus and the Latin noun equus (“horse”), since both of them appear in our language with the base equ-. If Julius Caesar should be suddenly brought back to life today, he might think that the mysterious English word equator referred to a horseback rider, or that equidistant meant that you had a cheap seat at the Kentucky Derby.

Solus and sanus, with their derivatives sole and sane, illustrate a fairly common type of morphological change, where the English word is the Latin base plus silent –e (see §14, 3.a). Further examples are amplus, curvus, and pronus (with its opposite, supinus). The development of Latin sanus to English sane shows also a semantic change: the meaning has been specialized, since Latin sanus involved both physical and mental health. The poet Juvenal said that all of us should pray for a healthy mind in a healthy body—mens sana in corpore sano.

Quite a few Latin adjectives ending in –ius and –uus have entered English as adjectives in –ious and –uous. Vacuus > vacuous is one case in point. Further examples include varius > various, pius > pious (and its opposite im-pius[3] > impious), spurius (originally, “illegitimate”) > spurious, noxius (“harmful”) > noxious, in-nocuus > innocuous, and strenuus > strenuous.

As in the case of 2nd declension nouns in –us (see §13), there is a small subtype of 1st and 2nd declension adjectives with –er in the masculine singular:

liber, libera, liberum
miser, misera, miserum
 wretched, miserable
pulcher, pulchra, pulchrum
sacer, sacra, sacrum
integer, integra, integrum
 untouched, whole

Some of these, like liber and miser, keep the vowel –e– in their base (and therefore in their English derivatives). Others drop the –e-, having bases like pulchr-, sacr-, and integr-. Notice that miser and integer are two English noun derivatives from this list. English sinister is the masculine form of a Latin adjective that meant “left-handed”; throughout human history, southpaws have always been abused linguistically.


  1. The phrase magnum opus may help you remember that opus is a neuter noun. It also shows that a Latin adjective is not likely to rhyme with its noun if the noun belongs to a different declension.
  2. We often use this noun adjectivally in expressions like “vacuum cleaner” and “vacuum bottle.” English is a language where words can jump casually from one grammatical function (part of speech) to another without any change in form. The word home is obviously a noun (“my old home”), but we use it as an adverb in “I’m going home,” and as an adjective in “home town” or “home run.” In highly inflected languages like Latin, words normally can’t switch functions without some change in form.
  3. This is our first example of the negative PREFIX in-, of which we’ll see much more later.


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Greek and Latin Roots: Part I - Latin Copyright © 2016 by Peter Smith (Estate) is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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