Latin Adjectives and Agreement: bonus, bona, bonum

A Latin adjective agrees with its noun in case, number and gender, and in nothing else. It does not have to share the noun's declension, so the two often look nothing alike: magna pars, a great part, is perfect Latin because both words are feminine.

The two families on one screen

Family one has three nominatives, family two has two (or, in the one-ending type, a single one). Either way, the ending follows the noun's gender.

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1. 1domus alba
2. 2canis albus
3. 3feles nigra

Domus looks like dominus but is feminine, so the white house is alba; the dog is masculine, albus. Niger drops its e in the feminine: the black cat is nigra.

Family one: bonus, bona, bonum

The masculine is dominus, the feminine is terra, the neuter is verbum: nothing new to learn. Singular:

Plural:

• Dominus bonus est. - The master is good.
• Terra magna est. - The land is large.
• Multa verba dicit. - He says many words.

Most of the common adjectives run this way:

Family two: fortis, forte

Third-declension endings, with one form for masculine and feminine together and a separate neuter.

Omnis, omne, all, every, runs on this, and so do gravis, heavy, and brevis, short. Three things mark the family:

The ablative is the one that catches people. A third-declension noun takes -e; a third-declension adjective takes -i, even on the same word pair:

• cum rege forti - with a brave king

One-ending adjectives: ingens, ingentis

These share a single nominative singular across all three genders, so the dictionary gives the genitive to show the stem. After that they are fortis:

• Urbs ingens est. - The city is huge.
• Urbem ingentem video. - I see a huge city.
• Felix es. - You are lucky.

A few, such as vetus, veteris, old, are not i-stems and take -e, -um and neuter -a: cum amico vetere, with an old friend.

Agreement is about categories, not sounds

Parse each word on its own, then compare the three labels. If case, number and gender match, the pair agrees, whatever the letters do:

Change the noun's case, and the adjective follows it:

Gender comes from the noun, not its ending

Third-declension nominatives are a poor guide to gender, so learn it with the noun. The adjective shows what you learned:

The -er adjectives

A handful of family-one adjectives have a masculine in -er. The feminine tells you whether the e survives: misera keeps it, sacra drops it.

Where adjectives sit

An adjective normally follows its noun; in front, it is emphasised. Quantity and size words normally lead:

• vir bonus - a good man
• multi homines - many people
• Magnam video urbem. - I see a great city.

In the last one, agreement holds magnam and urbem together across the verb. Poets stretch that gap to half a line. More in Latin word order.

Adjectives with no noun

Latin happily drops the noun and lets the adjective stand in for it: boni, good men; omnia, all things. That has its own page.

Mistakes English speakers make

What to do next

1. Learn every noun with its gender: pars, partis (f).
2. Run the drill below: sort by gender, then spot the mismatch.
3. Next, the perfect endings: what happened.