V peněžence mám jen jednu minci, proto platím kartou.

Because the preposition v meaning in requires the locative case when it describes location.

• basic form: peněženka = wallet
• after v for location: v peněžence = in the wallet

So:

• peněženka = nominative dictionary form
• v peněžence = locative singular

This is a very common Czech pattern:

• v domě = in the house
• v autě = in the car
• v peněžence = in the wallet

Czech often leaves out subject pronouns when they are obvious from the verb ending.

• mám = I have
• platím = I pay / I am paying

The -m ending already shows the subject is I, so saying já is usually unnecessary unless you want extra emphasis or contrast.

For example:

• Mám jen jednu minci. = I have only one coin.
• Já mám jen jednu minci. = I have only one coin.
  (emphatic, maybe contrasting with someone else)

Because jednu minci is the direct object of mám, so it has to be in the accusative case.

The noun mince is feminine, so the numeral one must also match it in gender and case:

• nominative: jedna mince
• accusative: jednu minci

So:

• mám jednu minci = I have one coin

Both words change:

• jedna → jednu
• mince → minci

Because mince is a feminine noun, and here it is in the accusative singular.

For many feminine nouns of this type, the ending changes like this:

• nominative singular: mince
• accusative singular: minci

So:

• To je mince. = That is a coin.
  (mince = subject, nominative)
• Mám minci. = I have a coin.
  (minci = object, accusative)

This kind of ending change is something Czech learners see a lot, especially with feminine nouns.

All three can mean only.

In this sentence, jen means only:

• mám jen jednu minci = I have only one coin

Very roughly:

• jen = only
• jenom = only, a bit fuller/more conversational sounding
• pouze = only, often a bit more formal or neutral

In many everyday sentences, jen and jenom are interchangeable:

• Mám jen jednu minci.
• Mám jenom jednu minci.

Both are natural.

Because the sentence has two clauses:

• V peněžence mám jen jednu minci
• proto platím kartou

The word proto means something like therefore / that’s why / so, and Czech normally separates these linked clauses with a comma.

So the comma marks the boundary between:

1. the reason/situation
2. the result

It is similar to English punctuation in a sentence like:

• I only have one coin in my wallet, so I’m paying by card.

Here proto means therefore, that’s why, or so.

It introduces the consequence of the first clause:

• V peněžence mám jen jednu minci, proto platím kartou.
• I only have one coin in my wallet, therefore / so / that’s why I’m paying by card.

It is a very useful linking word in Czech for expressing cause and result.

Compare:

• Je pozdě, proto jdu domů. = It’s late, so I’m going home.
• Nemám hotovost, proto platím kartou. = I don’t have cash, so I’m paying by card.

Because kartou is in the instrumental case, which is used here to express the means or method of payment.

So:

• platím kartou = I pay by card / with a card

You are not paying the card; you are using the card as the instrument.

That is why karta changes to kartou:

• nominative: karta
• instrumental: kartou

This is a very common pattern:

• píšu perem = I write with a pen
• jedu vlakem = I go by train
• platím kartou = I pay by card

Normally, no. In this sentence, Czech uses the instrumental without a preposition.

So the natural form is:

• platím kartou

Using s kartou would literally mean with the card, but not in the normal pay by card sense. Czech expresses the method directly through the instrumental case.

So remember:

• platit kartou = to pay by card

not usually

• platit s kartou

Yes, both are possible. Czech word order is much more flexible than English word order.

• V peněžence mám jen jednu minci.
• Mám v peněžence jen jednu minci.

Both are grammatical, but they place emphasis a little differently.

V peněžence mám... starts with the location, so it sets the scene first:
In my wallet, I have...

This often sounds natural when the speaker wants to focus first on where.

Mám v peněžence... starts with the verb, which is also fine and may feel a bit more neutral in some contexts.

Czech often moves words around to manage emphasis, topic, and flow rather than because of strict word-order rules.

Yes, platím is present tense.

In Czech, the present tense of an imperfective verb can often correspond to either:

• I pay
• I am paying

depending on context.

Here, because of the situation described, it most naturally means:

• I’m paying by card or
• I pay by card

In this sentence, English would usually prefer I’m paying by card, because it sounds like a specific current situation.

So:

• platím = present tense, 1st person singular
• verb: platit = to pay

Because Czech normally expresses possession with the verb mít = to have, just like English.

So:

• mám jednu minci = I have one coin

The phrase v peněžence just adds location:

• V peněžence mám jen jednu minci. = In my wallet, I have only one coin.

Czech does sometimes use je / jsou structures in other situations, but for simple possession, mít is the normal and easiest pattern.

Kartou is instrumental singular of karta.

Here is the basic change:

• nominative: karta
• instrumental: kartou

The instrumental case is often used after no preposition to show the tool, means, or method by which something is done.

In this sentence:

• platím kartou = I pay by card

So kartou tells you how the payment is made.