Estic cansada avui.

Because Catalan usually uses estar for temporary states or conditions, and being tired is treated as a temporary condition.

• estic = I am from estar
• sóc = I am from ser

So:

• Estic cansada = I am tired
• Sóc catalana = I am Catalan
• Sóc professora = I am a teacher

A very common learner point is that Catalan, like Spanish, has two verbs meaning to be, and cansada normally goes with estar.

Estic is:

• 1st person singular
• present tense
• from the verb estar

So it means I am.

A quick mini-paradigm:

• estic = I am
• estàs = you are
• està = he/she/it is
• estem = we are
• esteu = you all are
• estan = they are

Because the adjective agrees with the speaker’s gender.

• cansada = used by a feminine speaker
• cansat = used by a masculine speaker

So:

• A woman would normally say Estic cansada avui.
• A man would normally say Estic cansat avui.

Catalan adjectives often change form to match gender and number.

No. Catalan usually drops subject pronouns when they are clear from the verb form.

So Estic cansada avui already means I am tired today.
You can add jo for emphasis or contrast:

• Jo estic cansada avui, però ella no. = I’m tired today, but she isn’t.

This is very normal in Catalan, because the verb ending already tells you who the subject is.

Yes, avui can move. Catalan word order is fairly flexible.

All of these are possible:

• Estic cansada avui.
• Avui estic cansada.
• Estic avui cansada. — possible, but less natural in many everyday contexts

The most natural choices are usually:

• Estic cansada avui
• Avui estic cansada

Putting avui first often gives it a little more emphasis, like Today, I’m tired.

In this sentence, cansada functions as an adjective meaning tired.

Historically, it is related to a past participle, but here you should think of it as an adjective describing the subject.

That is why it agrees in gender and number:

• cansat = masculine singular
• cansada = feminine singular
• cansats = masculine plural
• cansades = feminine plural

Examples:

• Estem cansats. = We are tired (masculine or mixed group)
• Estan cansades. = They are tired (feminine group)

Yes, absolutely.

Both are correct:

• Estic cansada avui
• Avui estic cansada

The difference is mostly emphasis and rhythm:

• Avui estic cansada highlights today
• Estic cansada avui sounds more like a neutral statement, with today added at the end

In normal conversation, both are very natural.

A simple learner-friendly pronunciation is:

es-TEEK kun-ZAH-duh uh-VWEE

A few useful notes:

• Estic has stress on the last syllable: -tic
• cansada has stress on sa
• avui is stressed on the second syllable: vui

The u in avui combines with the following sound, so it may feel a bit like ah-VWEE.

Yes. molt means very, so this is a very natural expansion:

• Estic molt cansada avui. = I am very tired today.

This is useful because Catalan often uses molt where English uses very.

Other common expansions:

• Estic una mica cansada avui. = I’m a little tired today.
• Estic bastant cansada avui. = I’m quite tired today.

In this sentence, avui clearly means today.

In general, avui is the normal word for today.
If you want nowadays, Catalan more often uses expressions like:

• avui dia = nowadays
• actualment = currently

So Estic cansada avui is understood as I’m tired today, not I’m tired nowadays.