Learn Hardcore Polish: Mam więcej kluczy.

After więcej you always put the noun in the genitive case. The nominative plural of klucz is klucze, but the genitive plural is kluczy, so “Mam więcej kluczy” uses the genitive form.

What case does więcej require and why?

więcej is a quantifier that always takes the genitive case for whatever follows. It doesn’t matter whether the noun is countable or not; you decline it in genitive (singular or plural, depending on the noun).

How do you form the genitive plural of klucz?

klucz is a masculine inanimate noun with an irregular genitive plural. You remove the nominative -e ending and add -y, but because of the cz ending you get kluczy. In general, many masculine nouns ending in -cz form genitive plural with -czy (e.g. grosz → groszy, rzecz → rzeczy).

Why is there no niż (“than”) in “Mam więcej kluczy”?

The comparison is implied by context (e.g. “more than before” or “more than someone else already mentioned”). If you want to state the second element explicitly, you add niż. For example:

Mam więcej kluczy niż ona. (“I have more keys than she does.”)

When do you use więcej vs bardziej?

Use więcej to compare quantities of nouns (e.g. więcej wody, więcej książek). Use bardziej to compare qualities described by adjectives or adverbs (e.g. bardziej interesujący, bardziej intensywnie). You cannot say bardziej kluczy.

Why is the subject pronoun ja omitted in “Mam więcej kluczy”?

In Polish the verb ending (here -am in mam) already signals “I” (1st person singular). The pronoun ja is therefore redundant and usually dropped unless you want extra emphasis:

Ja mam więcej kluczy. (stress on “I”)

What is the typical word order in “Mam więcej kluczy,” and can it change?

The neutral order is Subject–Verb–Object, though the subject (ja) is omitted:
1) (Ja) mam (verb) więcej kluczy (object).
You can rearrange for emphasis:

Ja mam więcej kluczy (emphasize “I”)
Więcej kluczy mam (emphasize “more keys”)

How do you pronounce więcej kluczy? Where’s the stress and what are the key sounds?

Stress is on the penultimate syllable in Polish words:

więcej → VYEN-chey (phonetic: [ˈvjɛn.t͡ʂɛj])
kluczy → KLOO-chee (phonetic: [ˈklu.t͡ʂɨ])
Notes: ę before cj sounds like [ɛn], cz is [t͡ʂ], y is a close central vowel.

Is posiadam więcej kluczy the same as mam więcej kluczy?

Meaning-wise they are identical: both mean “I have more keys.” However, posiadam is more formal/literal (“I possess”), while mam is the everyday verb for “have.”