Když nemám hotovost, platím kartou.

It can work like both, depending on context.

In a sentence like this, když introduces a condition or repeated situation:

• Když nemám hotovost, platím kartou.

In English, that could be:

• When I don’t have cash, I pay by card.
• If I don’t have cash, I pay by card.

The Czech sentence is natural for a general habit, so when is often the best translation, but if is also understandable.

Because když nemám hotovost is a subordinate clause, and Czech separates subordinate clauses with commas.

So:

• Když nemám hotovost, platím kartou.

If you reverse the order, you still keep the comma:

• Platím kartou, když nemám hotovost.

Because Czech verbs usually already show who the subject is.

• nemám = I don’t have
• platím = I pay

So já is not necessary unless you want emphasis or contrast.

For example:

• Když nemám hotovost, platím kartou. = neutral
• Když já nemám hotovost, platím kartou. = more emphatic, like when I don’t have cash...

It comes from mít, which means to have.

• mám = I have
• nemám = I don’t have

The negative is formed with ne-:

• mám → nemám

It is in the accusative, because mít / nemít takes a direct object.

So in:

• nemám hotovost

hotovost is the thing you do not have.

The reason it looks unchanged is that for this noun type, the nominative and accusative singular are the same:

• nominative: hotovost
• accusative: hotovost

So the case is different, but the form happens to stay the same.

Hotovost means cash.

It refers to money in the form of banknotes and coins, not money in your bank account.

A useful contrast:

• nemám hotovost = I don’t have cash
• platím v hotovosti = I pay in cash

So:

• hotovost = cash
• v hotovosti = in cash

Because kartou is the instrumental singular of karta.

Czech often uses the instrumental case to express the means or tool by which something is done.

So:

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

Here are the forms:

• karta = nominative
• kartou = instrumental

No. In Czech, the normal expression is simply:

• platit kartou

English usually needs a preposition:

• pay by card
• pay with a card

But Czech does not use one here. The instrumental case already carries that meaning.

Because platím is the imperfective verb, and it fits a habitual or repeated action.

This sentence describes what you generally do:

• When I don’t have cash, I pay by card.

So platím is correct.

By contrast, zaplatím is perfective and usually refers to a single completed payment, often with future meaning:

• Zaplatím kartou. = I’ll pay by card.

So:

• platím = I pay / I am paying / I usually pay
• zaplatím = I will pay / I’ll pay once, as a completed action

No, Czech word order is flexible.

The original sentence:

• Když nemám hotovost, platím kartou.

is very natural and neutral.

You can also say:

• Platím kartou, když nemám hotovost.

The meaning stays basically the same, but the focus changes a little. The original version puts the condition first, which is common and clear.

Czech does not have articles.

So Czech simply says:

• hotovost
• kartou

without words corresponding to a, an, or the.

English needs articles or article-like wording, but Czech relies on context instead.

Yes. Kartou by itself usually means by card, in a general sense.

If you want to be more specific, you can say:

• platební kartou = by payment card / bank card
• kreditní kartou = by credit card
• debetní kartou = by debit card

But in everyday speech, just kartou is very common.

A simple pronunciation guide is:

• Když — roughly gdyzh
• nemám — NE-maam
• hotovost — HO-to-vost
• platím — PLA-teem
• kartou — KAR-toh

Two useful things to remember:

• Czech stress usually falls on the first syllable.
• Long vowels matter, so á and í are pronounced longer than short vowels.