Říkám mu, že dnes nemám čas.

Říkám is the 1st person singular present tense form of říkat, which means to say / to tell.

So:

• říkat = to say, to tell
• říkám = I say / I am saying / I tell

The ending -ám is the present-tense ending for I in this verb.

In this sentence, Říkám mu... means I’m telling him... or I tell him..., depending on context.

This is about aspect, which is very important in Czech.

• říkat = imperfective
• říct = perfective infinitive
• řeknu = I will say / I say once and complete it

Czech often uses the imperfective říkat when focusing on the act of speaking, especially in a more ongoing or descriptive way.

So:

• Říkám mu, že... = I’m telling him that...
• Řeknu mu, že... = I’ll tell him that... or I’ll say to him that...

In your sentence, říkám sounds natural for describing what you are saying to him.

Mu means to him.

It is the dative case form of the pronoun on (he).

So:

• on = he
• mu = to him

The verb říkat usually takes:

• the person you say something to in the dative
• the thing you say as a clause or object

So:

• Říkám mu... = I tell him...
• literally: I am saying to him...

Yes, but the meaning and emphasis change slightly.

• mu = normal, unstressed to him
• jemu = stressed or emphatic to him

So:

• Říkám mu, že dnes nemám čas. = neutral
• Říkám jemu, že dnes nemám čas. = more like I’m telling him, not someone else

In everyday neutral speech, mu is the usual choice.

Že means that.

It introduces a subordinate clause:

• Říkám mu = I tell him
• že dnes nemám čas = that today I don’t have time

So the structure is:

• I tell him + that-clause

In Czech, že is extremely common for reported speech and statements.

Because Czech normally uses a comma before a subordinate clause introduced by words like že.

So:

• Říkám mu, že dnes nemám čas.

This is standard Czech punctuation.

English sometimes drops that, but Czech still uses že here, and the comma is expected.

Nemám means I do not have / I don’t have.

It comes from the verb mít (to have):

• mám = I have
• nemám = I do not have

Czech usually forms negation by adding ne- to the verb:

• mám → nemám
• řeknu → neřeknu
• jsem → nejsem

So:

• dnes nemám čas = today I don’t have time

Because čas is the direct object of mít (to have), so it is in the accusative case.

However, čas is a masculine inanimate noun, and for many masculine inanimate nouns, the accusative singular looks the same as the nominative singular.

So:

• nominative: čas
• accusative: čas

That is why the form does not change.

Because Czech has no articles.

There is no direct equivalent of English a/an/the in normal grammar.

So:

• nemám čas can mean I don’t have time
• depending on context, English may need the, enough, or nothing extra

Czech leaves that kind of definiteness unstated unless it really needs to be clarified in some other way.

Dnes means today.

It is an adverb of time. In this sentence:

• že dnes nemám čas = that today I don’t have time

Its position is natural and neutral here, but Czech word order is fairly flexible.

You may also hear different word orders depending on emphasis, for example:

• Říkám mu, že dnes nemám čas. = neutral
• Říkám mu, že nemám dnes čas. = possible, a bit different in emphasis
• Dnes mu říkám, že nemám čas. = emphasis on today

The original version is very natural.

It can change more than in English.

Czech word order is flexible because grammatical roles are often shown by case endings, not just position. But different word orders create different emphasis.

Neutral version:

• Říkám mu, že dnes nemám čas.

Possible variants:

• Mu říkám, že dnes nemám čas.
  Emphasizes to him
• Dnes mu říkám, že nemám čas.
  Emphasizes today
• Že dnes nemám čas, říkám mu.
  Strongly marked, literary or contrastive

So the original sentence is the most straightforward everyday order.

Ř is one of the hardest Czech sounds for English speakers.

It is a special Czech sound, something like a mix of:

• r
• and a soft zh sound (like the s in measure)

You do not need perfect pronunciation immediately, but here is a rough guide:

• Říkám sounds approximately like rzhee-kaam or rzhii-kaam
• the ř should be trilled or vibrated more than English r

A practical learner tip: If true ř is too difficult at first, a slightly imperfect version is still understandable. Many learners start with something between r and ž.

Yes. Nemám čas is the normal and very common Czech way to say I don’t have time.

It is used just like in English:

• Dnes nemám čas. = I don’t have time today.
• Promiň, nemám čas. = Sorry, I don’t have time.

So this is a very useful everyday phrase to remember as a whole chunk.

Yes. Czech present tense often covers both ideas, and English chooses the best wording from context.

So Říkám mu... can be translated as:

• I tell him...
• I’m telling him...
• I say to him...

In natural English, I’m telling him that I don’t have time today is often the most idiomatic translation in context, but the Czech form itself does not force only one English option.