1. Latin Adjectives I. Overview
Adjectives are another part of speech, that is, another type of word (as opposed to a part of a sentence). The function of adjectives is to modify nouns or pronouns.

2. Latin Adjectives I. Overview
NB: Adjectives are words whose specific function is to modify nouns and pronouns.
But as we have already seen, prepositional phrases and words that are not adjectives can also be used to modify nouns.
Such words or prepositional phrases are said to behave adjectivally, but they are not of the same part of speech as adjectives and so they do not behave according to the same rules as proper adjectives in Latin.

3. Latin Adjectives I. Overview NB: Exempla Roma urbs Romanorum est.
Rome is the city of the Romans.
Transit puer hortum servi.
The boy goes through the garden of the slave.
Amor dei magnus est.
The love of God is great.

4. Latin Adjectives I. Overview
The form of an adjective in Latin is determined by the
1. GENDER
2. NUMBER
3. CASE
Of the noun it modifies.
In Latin, there are two types of adjectives:
1. 1st and 2nd Declension Adjectives
2. 3rd Declension Adjectives
Adjectives fall into one of these two groups depending on which noun declension(s) they take their endings from.

5. Latin Adjectives II. 1st and 2nd Declension Adjectives
1st and 2nd Declension adjectives are so called because they borrow the endings of the 1st and 2nd Declension.
Your dictionary shows you this by listing such adjectives like so:
Laetus, Laeta, Laetum
This listing tell us that the adjective has 3 sets of endings, based on the 1st Declension Feminine and 2nd Declension Masculine and Neuter.
Which set of endings an adjective uses is determined by the gender of the noun it modifies.

6. Latin Adjectives II. 1st and 2nd Declension Adjectives
The following chart explains which set of declensional ending a noun of the 1st and 2nd Declension uses according to the gender of its noun:
Noun Gender Declension Pattern
Feminine  1st Declension Endings
Masculine  2nd Declension Masculine
Endings
Neuter  2nd Declension Neuter Endings

7. Latin Adjectives II. 1st and 2nd Declension Adjectives Exempla:
Puella Laeta Puer Laetus Somnium Laetum
Puellae Laetae Pueri Laeti Somnii Laeti
Puellae Laetae Puero Laeto Somnio Laeto
Puellam Laetam Puerum Laetum Somnium Laetum
Puellā Laetā Puero Laeto Somnio Laeto
Puellae Laetae Pueri Laeti Somnia Laeta
Puellarum Laetarum Puerorum Laetorum Somniorum Laetorum
Puellis Laetis Pueris Laetis Somniis Laetis
Puellas Laetas Pueros Laetos Somnia Laeta
Puellis Laetis Pueris Laetis Somniis Laetis

8. Latin Adjectives II. 1st and 2nd Declension Adjectives
Exempla: Note that the adjective matches the Gender, Number, and Case of the noun it modifies. The Gender, Number, and Case of the noun are determined by its function in the Sentence.
Mater filio parvo togam longam faciebat.
E silvis obscuris territi pueri currunt.
Miles frigidae aquae poculum magnum bibit.

9. Latin Adjectives II. 1st and 2nd Declension Adjectives
NB: All adjectives agree with the noun they modify in Gender, Number, and Case and ONLY GENDER, NUMBER, AND CASE.
This means an adjective WILL NOT always have the same ENDING as the Noun it modifies, as when the Declension of the noun and adjective are different. But the ending of the adjective ALWAYS signifies the same Gender, Number, and Case as the ending of the Noun.

10. Latin Adjectives II. 1st and 2nd Declension Adjectives NB: Exempla
Sorores pulchrae fratrem parvum amant.
Canem ferum e casā parvā miles fessus ducit.
Ingenioso consilio boni imperatoris milites strenui hostes vincunt.
Tertiā horā milites conditi in urbem tacitam intrant.

11. Latin Adjectives II. 1st and 2nd Declension Adjectives
NB: In all of the above examples, the ENDING of the ADJECTIVE is different from the ENDING of the NOUN. This is because the DECLENSION of the adjective is different from the DECLENSION of the NOUN.
WHAT MATTERS is that the GENDER, NUMBER, AND CASE OF THE NOUN AND ADJECTIVE ARE THE SAME, REGARDLESS OF THEIR ENDINGS.

12. Latin Adjectives II. 1st and 2nd Declension Adjectives NB: Exempla
Sorores pulchrae fratrem parvum amant.
F.N.P. F.N.P M.Ac.S. M.Ac.S.
Canem ferum e casā parvā miles fessus ducit.
M.Ac.S. M.Ac.S F.Ab.S. F.Ab.S. M.N.S. M.N.S
Ingenioso consilio boni imperatoris milites strenui
Ne.Ab.S. Ne.Ab.S. M.G.S. M.G.S. M.N.P. M.N.P.
hostes vincunt.
Tertiā horā milites conditi in urbem tacitam intrant.
F.Ab. F.Ab. M.N.P. M..N.P. F.Ac.S. F.Ac.S.
S. S.

13. Latin Adjectives II. 1st and 2nd Declension Adjectives
NB: Exemplum – Nauta and Validus, Valida, Valdum
Nauta Validus Nautae Validi
Nautae Validi Nautarum Validorum
Nautae Valido Nautis Validis
Nautam Validum Nautas Validos
Nautā Valido Nautis Validis

14. Latin Adjectives II. 1st and 2nd Declension Adjectives
NB: Exemplum – Canis and Ferus, Fera, Ferum
Canis Ferus Canes Feri
Canis Feri Canum Ferorum
Cani Fero Canibus Feris
Canem Ferum Canes Feros
Cane Fero Canibus Feris

15. Latin Adjectives II. 1st and 2nd Declension Adjectives
NB: Exemplum – Carmen and Pulcher, Pulchra, Pulchrum
Carmen Pulchrum Carmina Pulchra
Carminis Pulchri Carminum Pulchrorum
Carmini Pulchro Carminibus Pulchris
Carmine Pulchro Carminibus Pulchris

16. Latin Adjectives III. 3rd Declension Adjectives
3rd Declension adjectives are so called because they borrow the endings of 3rd Declension.
There are three types of 3rd Declension adjectives, grouped according to how many different ending patterns the adjective uses:
1. One Termination: The Masculine, Feminine, and Neuter Nominative forms are all the same.
2. Two Terminations: The Masculine and Feminine Nominative forms are the same, but the Neuter Nominative is different.
3. Three Terminations: The Masculine, Feminine, and Neuter Nominative forms are all different.

17. Latin Adjectives  - i  - i III. 3rd Declension Adjectives
NB: The endings of 3rd Delcension ADJECTIVES are slightly different from the endings of 3rd Declension NOUNS:
M/F N
[ ] [Same as Acc]
- is is
- i - i
- em [Same as Nom]
 - i  - i
- es  - ia
 - ium  - ium
- ibus - ibus

18. Latin Adjectives III. 3rd Declension Adjectives
The way an adjective is listed in your dictionary tells you both whether an adjective belongs to the 3rd Declension and which of the three types it is:
1. If it is of One Termination, the adjective will be listed with its Nominative and Genitive Singular.
Exemplum:
Felix, Felicis
Nom. S. Gen. S.
By listing the adjective with only the Nominative and then the Genitive, your dictionary is telling you that there is only one form of the Nominative.
As always, you can tell that the word belongs to the 3rd Declension because the Genitive Singular ends in –is.

19. Latin Adjectives III. 3rd Declension Adjectives 1. One Termination
M/F N M/F N
Felix Felices Felicia
Felicis Felicium
Felici Felicibus
Felicem Felix Felices Felicia

20. Latin Adjectives III. 3rd Declension Adjectives
2. If an adjective is of Two Terminations, the adjective will be listed with the Masculine, Feminine, and Neuter Nominative forms:
Exemplum:
Fortis, Fortis, Forte
M.Nom.S. F.Nom.S. N.Nom.S.
By listing the adjective in this way, your dictionary is telling you that this adjective has only two different forms of the Nominative, and that the Masculine and Feminine Nominative are the same.
All Adjectives ending in –is, -is, -e are 3rd Declension.

21. Latin Adjectives III. 3rd Declension Adjectives 2. Two Terminations
M F N
Fortis Fortis Forte
Fortis Fortis Fortis
Forti Forti Forti
Fortem Fortem Forte
Fortes Fortes Fortia
Fortium Fortium Fortium
Fortibus Fortibus Fortibus

22. Latin Adjectives III. 3rd Declension Adjectives
3. If an adjective is of Three Terminations, the adjective will be listed with the Masculine, Feminine, and Neuter Nominative forms:
Exemplum:
Acer, Acris, Acre
M.Nom.S F.Nom.S. N.Nom.S.
By listing the adjective in this way, your dictionary is telling you that this adjective has three different forms of the Nominative, and that the Masculine, Feminine, and Neuter Nominative are different.

23. Latin Adjectives III. 3rd Declension Adjectives 3. Three Terminations
M F N
Acer Acris Acre
Acris Acris Acris
Acri Acri Acri
Acrem Acrem Acre
Acres Acres Acria
Acrium Acrium Acrium
Acribus ` Acribus Acribus
Acribus Acribus Acribus

24. Latin Adjectives III. 3rd Declension Adjectives
NB: As with Nouns, what defines an adjective as belonging to the 3rd Declension is the fact that the GENITIVE SINGULAR ending is –is.
THIS IS ALWAYS TRUE OF 3RD DECLENSION ADJECTIVES, REGARDLESS OF WHETHER THEY HAVE ONE, TWO, OR THREE TERMINATIONS.

25. Latin Adjectives III. 3rd Declension Adjectives
NB: As always, a 3rd Declension Adjective agrees with its noun in GENDER, NUMBER, AND CASE, EVEN IF THE ENDINGS OF THE NOUN AND ADJECTIVE ARE NOT THE SAME.

26. Latin Adjectives III. 3rd Declension Adjectives
Exempla: One Termination
Puer Felix Puella Felix Somnium Felix
Pueri Felicis Puellae Felicis Somnii Felicis
Puero Felici Puellae Felici Somnio Felici
Puerum Felicem Puellam Felicem Somnium Felix
Puero Felici Puellā Felici Somnio Felici
Pueri Felices Puellae Felices Somnia Felicia
Puerorum Felicium Puellarum Felicium Somniorum Felicium
Pueris Felicibus Puellis Felicibus Somniis Felicibus
Pueros Felices Puellas Felices Somnia Felicia
Pueris Felicibus Puellis Felicibus Somniis Felicibus

27. Latin Adjectives III. 3rd Declension Adjectives
Exempla: One Termination
NB: The Masculine, Feminine, and Neuter Nominative singular forms of the adjective are all the same. That is, the adjective has only one termination.
The Neuter Accusative Singular and the Neuter Nominative and Accusative Plural all differ from those forms of the Masculine and Feminine.
In all other cases, however, the forms of the Masculine, Feminine, and Neuter are all the same.

28. Latin Adjectives III. 3rd Declension Adjectives
Exempla: Two Terminations
M F N
Puer Fortis Puellae Fortis Somnium Forte
Pueri Fortis Puellae Fortis Somnii Fortis
Puero Forti Puellae Forti Somnio Forti
Puerum Fortem Puellam Fortem Somnium Forte
Puero Forti Puellā Forti Somnio Forti
Pueri Fortes Puellae Fortes Somnia Fortia
Puerorum Fortium Puellarum Fortium Somniorum Fortium
Pueris Fortibus Puellis Fortibus Somniis Fortibus
Pueros Fortes Puellas Fortes Somnia Fortia

29. Latin Adjectives III. 3rd Declension Adjectives
Exempla: Two Terminations
NB: The Nominative Masculine and Feminine singular forms of the adjective are the same, but the Nominative Neuter Singular form is different. That is, the adjective has two terminations.
The Neuter Accusative Singular and the Neuter Nominative and Accusative Plural all differ from those forms of the Masculine and Feminine.
In all other cases, however, the forms of the Masculine, Feminine, and Neuter are all the same.

30. Latin Adjectives III. 3rd Declension Adjectives
Exempla: Three Terminations
M F N
Puer Acer Puella Acris Somnium Acre
Pueri Acris Puellae Acris Somnii Acris
Puero Acri Puellae Acri Somnio Acri
Puerum Acrem Puellam Acrem Somnium Acre
Puero Acri Puellā Acri Somnii Acri
Pueri Acres Puellae Acres Somnia Acria
Puerorum Acrium Puellarum Acrium Somniorum Acrium
Pueris Acribus Puellis Acribus Somniis Acribus
Pueros Acres Puellas Acres Somnia Acria

31. Latin Adjectives III. 3rd Declension Adjectives
Exempla: Three Terminations
NB: The Masculine, Feminine, and Neuter nominative singular forms of the adjective are all different. That is, the adjective has two terminations.
The Neuter Accusative Singular and the Neuter Nominative and Accusative Plural all differ from those forms of the Masculine and Feminine.
In all other cases, however, the forms of the Masculine, Feminine, and Neuter are all the same.

32. Latin Adjectives III. 3rd Declension Adjectives Exempla: Sententiae
Pueri fortes equum infelicem agebant.
N.M.Pl. N.M.Pl. Ac.M.S. Ac.M.S.
2nd D. 3rd D nd D. 3rd D.
E pugnā feroci miles incolumnis venit.
F.Ab.S. F.Ab.S. M.N.S. M.N.S.
1st D rd D rd D rd D.

33. Latin Adjectives III. 3rd Declension Adjectives Exempla: Sententiae
Legio fessa trans flumnia magna et montes altos transit.
N.F.S N.F.S Ac.Ne.Pl. Ac.Ne.Pl. Ac.M.Pl. Ac.M.Pl.
3rd D. 1st+2nd D. 3rd D st+2nd D. 3rd D st+2nd D.

34. Latin Adjectives III. 3rd Declension Adjectives Exempla: Sententiae
NB: The above sentences feature several examples of 3rd Declension adjectives modifying a noun of the 1st, 2nd, or 3rd Declension, and of 1st and 2nd Declension adjectives modifying a 1st, 2nd, or 3rd Declension noun.
These examples demonstrate the fact that any type of adjective can be used to modify any type of noun. The Declension of the adjective in no way changes the form of the noun, and the Declension of the noun in no way changes the form of the adjective.

35. Latin Adjectives III. 3rd Declension Adjectives Exempla: Sententiae
NB: Remember, the form of a noun in a particular case is determined by the Declension and Gender of the noun.
In just the same way, the form of an adjective is determined by the Declension of the ADJECTIVE and the Gender of the NOUN.
AS ALWAYS, WHAT MATTERS is that the GENDER, NUMBER, AND CASE OF THE NOUN AND ADJECTIVE ARE THE SAME, REGARDLESS OF THEIR ENDINGS.