Describing Tools and Companions
Whenever you use a noun in the instrumental case—whether as a tool (without a preposition) or as company (with the preposition s or sa)—any adjectives describing it must also be in the instrumental case. To do this, you will need to change the adjective's ending to match the noun's gender and number.
Masculine and Neuter Singular
For masculine and neuter nouns in the singular, the adjective takes the ending -im.
| sharp | oštar |
| He works with a sharp tool. | On radi oštrim alatom. |
Notice how this ending applies both when describing a tool (which uses no preposition) and when describing a person you are with (which uses s or sa).
| We arrived with an experienced guide. | Došli smo s iskusnim vodičem. |
| We traveled by official car. | Putovali smo službenim automobilom. |
Feminine Singular
For feminine nouns in the singular, the adjective takes the ending -om. Because regular feminine nouns in the instrumental case also end in -om, the adjective and the noun will usually rhyme perfectly.
| He is playing with his favorite wooden toy. | On se igra s omiljenom drvenom igračkom. |
Plural Adjectives
Plural adjectives are the easiest to remember! Regardless of whether the noun is masculine, feminine, or neuter, plural adjectives in the instrumental case always take the ending -im.
| We eat with wooden spoons. | Jedemo drvenim žlicama. |
| He arrived with fun friends. | Došao je sa zabavnim prijateljima. |
| The director is talking with new clients. | Direktor razgovara s novim klijentima. |