La mare està cansada perquè hi ha feina avui.

In Catalan, estar is normally used for temporary states or conditions. Being tired is usually seen as temporary, so està cansada is the natural choice.

Ser is more often used for identity, essential qualities, or more permanent characteristics. So és cansada would sound unusual here.

Because adjectives in Catalan usually agree with the noun they describe in gender and number.

• mare = feminine singular
• so the adjective is also feminine singular: cansada

If the subject were masculine, you would usually get cansat.

Hi ha means there is or there are.

So:

• hi ha feina = there is work
• or more naturally in some contexts, there is work to do

It is best learned as a set expression. The hi is not usually translated separately in this structure.

Catalan often uses the definite article before family words in ordinary speech.

So la mare can mean:

• my mother
• mother
• mom

depending on context.

This is more natural in Catalan than the mother would be in English, so you should not translate the article too literally every time.

Both are related to work, but they are not always used in exactly the same way.

• feina often means work to do, tasks, or a job
• treball can be more general, like work, labor, or piece of work

In hi ha feina avui, feina is very natural because it suggests there is work waiting to be done today.

Because perquè means because.

Catalan distinguishes it from per què, which means why or for what in questions.

Compare:

• Està cansada perquè hi ha feina. = She is tired because there is work.
• Per què està cansada? = Why is she tired?

So the accent helps mark the meaning.

Avui means today, and Catalan allows fairly flexible word order.

Hi ha feina avui is completely natural. It simply places the time expression at the end.

You could also say:

• Avui hi ha feina

That version puts a bit more emphasis on today.

It works for both singular and plural, just like English there is / there are, though in everyday Catalan the same form hi ha is used in both cases.

Examples:

• Hi ha feina. = There is work.
• Hi ha problemes. = There are problems.

So in your sentence, it simply means that work exists or is present today.

In hi ha, the hi is usually pronounced roughly like ee.

So hi ha sounds approximately like ee ah.

The exact pronunciation can vary a little by dialect and speed of speech, but for a learner, thinking of hi ha as something close to ee-ah is a helpful start.