The Instrumental case answers the questions: Kim? (With/as whom?) and Czym? (With/as what?).

When to use Instrumental:

1. Identity / Profession (after "Być"): When you say who someone is.
2. Jestem studentem. (I am a student.)
3. Company (after "Z"): To say "with" someone.
4. Idę do kina z bratem. (I go to the cinema with brother.)
5. Transport: To say "by" means of transport.
6. Jadę autobusem. (I go by bus.)
7. Instrument: To say "with" a tool.
8. Piszę długopisem. (I write with a pen.)
9. Interests: After interesować się (to be interested in).

Personal Pronouns

Pronouns mostly end in nasal sounds (-ą) or -im.

Noun Endings (Singular)

A. Feminine Nouns 🎀

Rule: Change -a to -ą.

This is very consistent.

1. mama → z mamą.
2. kawa → z kawą.
3. noc (consonant) → z nocą.

B. Masculine & Neuter Nouns 👨👶

Rule: Add -em.

Standard Rule: Just add -em (or change vowel to -em).

1. brat → z bratem.
2. samochód → samochodem.
3. okno → pod oknem.
4. biuro → z biurem.

⚠️ Special Rule: The "K/G" Exception

If a Masculine noun ends in -k or -g, you must insert an -i- before the ending.

1. Polak → jestem Polakiem (not Polakem).
2. pieróg → z pierogiem.

Adjective Endings (Singular)

Adjectives must agree with the noun.

A. Feminine Adjectives

Rule: Change -a to -ą.

1. dobra → z dobrą.
2. nowa → z nową.

B. Masculine & Neuter Adjectives

Rule: The ending is -ym or -im.

When to use -ym? (Standard)

Use for most hard consonants (d, t, w, m, n, r, s, z, ł).

1. stary → ze starym.
2. nowy → z nowym.
3. dobry → z dobrym.

When to use -im? (Soft & K/G)

Use if the stem ends in k, g or a soft sound (n, ci, si).

1. polski → z polskim.
2. długi → z długim.
3. tani → z tanim.

The Plural (All Genders) 👯‍♂️

The Instrumental Plural is the easiest form in Polish grammar because Gender does not matter for the nouns.

Noun Rule: Always "-ami"

Regardless if it is men, women, dogs, or tables, the ending is -ami.

1. kobiety → z kobietami.
2. koledzy → z kolegami.
3. psy → z psami.
4. słowa → ze słowami.

Exception: A few words end in -mi (e.g., dzieci → z dziećmi, ludzie → z ludźmi).

Adjective Rule: "-ymi" vs "-imi"

Just like the singular, you must choose based on the stem sound.

1. -ymi: Hard consonants.
2. nowe → z nowymi.
3. dobre → z dobrymi.
4. -imi: K, G, and Soft sounds.
5. polskie → z polskimi.
6. wysokie → z wysokimi.

Summary Tables & Examples

Here is how to modify Nouns, Adjectives (dobry/polski), Demonstratives (ten), and Possessives (mój).

Singular Table

Examples (Singular):

1. Jestem nowym pracownikiem. (I am a new employee.)
2. Masc: nowy → nowym, pracownik (ends in k) → pracownikiem.
3. Idę z tą piękną dziewczyną. (I go with this beautiful girl.)
4. Fem: ta → tą, piękna → piękną, dziewczyna → dziewczyną.
5. Jem długim widelcem. (I eat with a long fork.)
6. Masc: długi (g) → długim, widelec → widelcem.

Plural Table

Examples (Plural):

Rozmawiam z moimi sąsiadami. (I talk with my neighbors.)

Bawię się klockami. (I play with blocks.)

Lubię ciastka z polskimi owocami. (I like cookies with Polish fruits.)

Read More about: Polish Cases, Polish Accusative, Polish Locative, Polish Dative, Polish Genitive, Polish Vocative