Learn Hardcore Czech: Hlavně nechci být nemocný. - Above all, I don't want to be ill.

“Mainly I don’t want to be sick” is understandable but sounds a bit odd in everyday English. In Czech, hlavně is very common as a sentence adverb meaning most importantly / above all.

Where can hlavně go in the sentence? Is Hlavně nechci být nemocný the only option?

The neutral, most common position is exactly as in your sentence:

Hlavně nechci být nemocný. – Above all, I don’t want to be ill.

Other possible positions:

Já hlavně nechci být nemocný.
– Me, above all, I don’t want to be ill.
Emphasises já (I), maybe contrasting with others.
Nechci být hlavně nemocný.
This changes the meaning to something like:
– I don’t want to be mainly sick (as opposed to some other thing).
It sounds strange unless you are contrasting “being sick” with other qualities (I don’t want my main problem to be that I’m sick). Usually not what is meant.
Nechci být nemocný hlavně.
This is very unnatural in modern Czech.

So, for the meaning “Above all, I don’t want to be sick”, hlavně at the beginning is best and most natural.

Why is it nechci být and not nechci jsem?

Because in Czech, after verbs like chtít (to want), you use the infinitive, not a finite form of the verb.

chtít + infinitive
- chci být – I want to be
- nechci být – I don’t want to be
- chce spát – he/she wants to sleep
- nechceme čekat – we don’t want to wait

Být is the infinitive of “to be”.
Jsem is the 1st person singular present form (I am), and you cannot say:

✗ nechci jsem – this is ungrammatical

So the correct pattern is:

(ne)chci + být + [adjective/noun]
- nechci být nemocný – I don’t want to be ill
- chci být lékař – I want to be a doctor

How is nechci formed from chtít (“to want”)?

The verb chtít is irregular. Its present tense (standard form) is:

já chci – I want
ty chceš – you (sg.) want
on/ona/ono chce – he/she/it wants
my chceme – we want
vy chcete – you (pl./formal) want
oni chtějí – they want

Negation is made by adding the prefix ne- to the verb:

chci → nechci – I don’t want
chceš → nechceš – you don’t want
chceme → nechceme – we don’t want

So nechci literally = I-want-not.

What grammatical form is nemocný, and why does it end in -ý?

Nemocný is an adjective meaning ill, sick. In this sentence it’s used as a predicate adjective after být (to be).

Here it is:

masculine
singular
nominative (the basic “dictionary” case)
agreeing with the (understood) subject já (I), assumed to be male

So:

A man: Hlavně nechci být nemocný.
A woman: Hlavně nechci být nemocná.

The -ý ending is the regular masculine singular nominative ending for many adjectives (dobrý, malý, velký, nemocný).

If a woman is speaking, does the sentence change?

Yes, a woman would normally change the adjective to the feminine form:

Hlavně nechci být nemocná.

Explanation:

masculine speaker → nemocný
feminine speaker → nemocná

The verb nechci stays the same; only the adjective changes to match the gender of the speaker.

Other examples:

(man) Jsem unavený. – I am tired.
(woman) Jsem unavená. – I am tired.

What’s the difference between být nemocný and onemocnět?

They describe different aspects of the situation:

být nemocný – to be ill, the state of being sick
- nechci být nemocný – I don’t want to be (in a sick state)
onemocnět – to fall ill, to become sick, the change into that state
- nechci onemocnět – I don’t want to get sick (I don’t want to catch an illness)

So:

Hlavně nechci být nemocný.
Focuses on being ill, experiencing that state.
Hlavně nechci onemocnět.
Focuses more on catching something, becoming ill in the first place.

In many contexts both could be used, but the nuance is slightly different.

Is there any difference between nemocný and nemocen?

Yes, mainly in style and frequency:

nemocný
- the normal, everyday adjective
- used in all types of speech: casual, neutral, formal
- být nemocný – to be ill
nemocen
- a short (pronominal) form of the adjective
- sounds more formal, old-fashioned, or literary
- more likely in written language, set phrases, or official contexts
- e.g. in older texts: Je nemocen. – He is ill.

In modern everyday speech, people almost always say:

Je nemocný., Jsem nemocný/nemocná.

So your sentence with nemocen:

Hlavně nechci být nemocen.

is grammatically correct, but would sound bookish or old-fashioned in normal conversation.

Is hlavně the same as opravdu (“really”)? How would I say “I really don’t want to be sick” instead?

They are not the same.

hlavně – above all, mainly, especially, the main thing is
- Hlavně nechci být nemocný.
  – Above all, I don’t want to be sick.
opravdu – really, truly
- Opravdu nechci být nemocný.
  – I really don’t want to be sick.

Compare:

Hlavně nechci být nemocný.
Main point among several: maybe you don’t mind other problems, but being sick is what you especially want to avoid.
Opravdu nechci být nemocný.
Emphasises the strength of your feeling – you truly, seriously don’t want to be sick.

You can also combine them for extra nuance:

Opravdu hlavně nechci být nemocný.
– I really mainly/above all don’t want to be sick.
(stylistically a bit heavy, but possible in spoken emphasis)

Why is negation attached to the verb (nechci) instead of using a separate word like “not”?

In Czech, the normal way to negate a verb is to add the prefix ne- directly to it. There is no separate word equivalent to English “not” placed after an auxiliary.

So:

chci – I want
nechci – I do not want
mám – I have
nemám – I do not have
chápu – I understand
nechápu – I do not understand

You cannot separate ne from the verb like in English:

✗ já ne chci být nemocný – wrong
✓ já nechci být nemocný – correct (I don’t want to be ill)

You can add já for emphasis:

Já nechci být nemocný. – I don’t want to be sick. (implying maybe someone else does)

Could this also mean “I don’t want to be a sick person” (like permanently ill), or is it just about being sick at some point?

On its own, Hlavně nechci být nemocný is understood as:

Above all, I don’t want to be ill (at least at some time / in this situation).

It normally refers to being ill as a state, not to a permanent identity as “a sick person”.

If you wanted to stress long-term or permanent illness, you’d usually add more information:

Hlavně nechci být dlouhodobě nemocný.
– Above all, I don’t want to be ill long-term.
Nechci být celý život nemocný.
– I don’t want to be sick my whole life.

So in everyday use, your sentence is about not wanting to be ill (to get sick) in general, not about defining yourself as “a sick person” permanently.