Latin Adjectives and Agreement: bonus, bona, bonum and fortis, forte

You have met the nouns. Now for the words that hang off them.

Latin adjectives are, mechanically, the easiest thing in the language, because they do not use any endings you have not already learned. What is hard about them is a single idea that English gives you no preparation for: an adjective agrees with its noun in case, number and gender, and in nothing else at all.

Get that, and adjectives cost you almost nothing. Miss it, and every second line of Latin looks broken.

The two families

Every adjective in this course belongs to one of two families, and you can tell which from the dictionary entry.

Family one is cited with three forms: bonus, bona, bonum. It borrows second-declension endings for the masculine and neuter and first-declension endings for the feminine. This family holds magnus, multus, malus, novus, verus, altus, parvus, longus, summus, sanctus, certus, tantus and most of the common adjectives you have met.

Look at it properly before you try to memorise it. There is nothing new in that table. The masculine column is dominus. The feminine column is terra. The neuter column is templum. If you know the first two declensions you already know this adjective, and drilling it as a fresh paradigm is wasted effort.

Family two is cited with two forms: fortis, forte. It uses third-declension i-stem endings, with one form covering masculine and feminine together and a separate neuter.

Omnis, omne runs on this, and so do gravis, brevis, dulcis, similis, nobilis, talis and civilis. Note the three i-stem markers: ablative singular -i, genitive plural -ium, neuter plural -ia. Third-declension nouns mostly take -e in the ablative singular (rege, corpore); third-declension adjectives take -i. That difference is small, real, and worth knowing before you meet forti animo.

There is a third shape inside family two, cited with one form plus its genitive: ingens, ingentis. Felix, felicis. Praesens, praesentis. All three genders share a nominative singular, and everything else is fortis with the stem the genitive gives you: ingentem, ingenti, ingentia, ingentium. It is a spelling variation, not a new pattern.

Agreement is about categories, not sounds

Here is the idea that costs beginners the most time.

Textbooks introduce adjectives with examples that rhyme. Bonus dominus. Bona puella. Bonum templum. The learner quietly concludes that agreement means the two words end the same way, and then reads a real sentence and falls over.

Agreement means matching case, number and gender. It does not mean matching declension, and it does not mean matching sound.

magna pars - a great part

Magna is a first-declension form and pars is a third-declension noun. They share not one letter of ending. Both are feminine nominative singular, so they agree.

forti animo - with a brave spirit

Forti is a third-declension adjective in the ablative singular. Animo is a second-declension noun in the ablative singular. Both masculine, both ablative, both singular. Perfect agreement, no shared letters.

omnium hominum - of all people

Both genitive plural. Omnium is an i-stem adjective, hominum a consonant-stem noun, so one has the -i- and the other does not. Still agreement.

The clean test is not "do these look alike" but "parse each word separately, then compare the three labels". Once that becomes automatic, Latin adjectives stop being a problem forever.

The -er adjectives, briefly

A handful of family-one adjectives have a masculine nominative in -er and then behave normally. The only question is whether the e survives into the stem, and the dictionary answers it:

• miser, misera, miserum - keeps the e: miseri, miserum, miseros.
• sacer, sacra, sacrum - drops it: sacri, sacrum, sacros.
• noster, nostra, nostrum - drops it, as does pulcher, pulchra, pulchrum and niger, nigra, nigrum.

Learn the feminine form and the question answers itself.

Adjectives with no noun

Latin drops the noun and lets the adjective stand in for it far more readily than English does. The gender tells you what to supply.

• Masculine plural means people: boni, good men. Mali, the wicked. Multi, many people. Nostri, our men.
• Neuter singular or plural means things: bonum, a good thing. Omnia, all things. Multa, many things. Vera, the truth.
• Feminine works too where the noun is obvious: nostra, our women.

This is not a poetic flourish. It is ordinary Latin, and it produces a great many of the phrases that survived into English:

summum bonum - the highest good

omnia vincit Amor - love conquers all things (Virgil)

If you meet an adjective sitting in a sentence with no noun anywhere that could match it, that is not a missing word. The adjective is the noun.

Where they sit

The word order article has the detail, but the short version: an adjective normally follows its noun, so vir bonus and urbs antiqua are the neutral order. Putting it in front is emphasis. The exception is quantity and size words, which normally lead: multi homines, magna pars, omnes viri, tanta res.

And because agreement is carried on the endings, the pair does not have to sit together. A poet can put magnam in the first foot of a line and urbem in the last, and the reader reassembles them without effort, because nothing else in the line is feminine accusative singular. English simply cannot do this.

What to take away

• Two families. Bonus, bona, bonum is recycled first and second declension. Fortis, forte is a third-declension i-stem.
• I-stem markers on the second family: ablative singular -i, genitive plural -ium, neuter plural -ia. Third-declension nouns take -e in the ablative; adjectives take -i.
• One-ending adjectives like ingens, ingentis and felix, felicis are fortis with a different nominative. Take the stem from the genitive.
• Agreement is case, number and gender. Never declension. Magna pars and forti animo are correct precisely because they do not rhyme.
• An adjective without a noun becomes one: boni is good men, omnia is all things.

Next: the pronouns, and the four little words - hic, ille, is and qui - that between them do more work than any noun in the language.