La cullera és petita, però el plat és molt gran.

Because Catalan nouns have grammatical gender.

• la cullera = feminine
• el plat = masculine

The article has to match the noun:

• el = the for masculine singular nouns
• la = the for feminine singular nouns

This does not always match natural gender. A spoon is not female, and a plate is not male; this is just a grammatical category.

A learner usually has to memorize the noun together with its article:

• la cullera
• el plat

That is often the easiest way to learn gender in Catalan.

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

Here, cullera is feminine singular, so the adjective also becomes feminine singular:

• masculine singular: petit
• feminine singular: petita
• masculine plural: petits
• feminine plural: petites

So:

• La cullera és petita. = The spoon is small.

If the noun were masculine, you would use petit:

• El plat és petit.

Some Catalan adjectives change form for gender, but some do not.

Gran is one of the adjectives that usually has the same form for masculine and feminine in the singular:

• el plat és gran
• la cullera és gran

In the plural, it changes to grans:

• els plats són grans
• les culleres són grans

So petit/petita changes for gender, but gran does not in the singular.

És means is. It is the third-person singular form of the verb ser (to be).

So:

• La cullera és petita. = The spoon is small.
• El plat és molt gran. = The plate is very big.

The accent matters because és and es are different words:

• és = is
• es = a pronoun, often like oneself / each other / him/her/it in certain structures

So the accent helps distinguish meanings.

Però means but.

The accent shows the correct stress and is part of the normal spelling of the word in Catalan. It is not optional.

So:

• La cullera és petita, però el plat és molt gran. = The spoon is small, but the plate is very big.

For an English speaker, it is best simply to memorize però as the standard Catalan word for but.

Here, molt means very.

It is modifying the adjective gran:

• molt gran = very big / very large

So:

• el plat és molt gran = the plate is very big

This can be confusing because molt can also mean much or a lot, depending on context.

Examples:

• molt gran = very big
• treballa molt = he/she works a lot
• molta aigua = a lot of water

In your sentence, since it comes before an adjective (gran), it means very.

Because in this sentence molt is being used as an adverb, not an adjective.

When molt modifies an adjective, adverb, or verb, it usually stays molt:

• molt gran = very big
• molt bé = very well
• treballa molt = works a lot

But when it modifies a noun, it behaves more like an adjective/determiner and agrees:

• molt pa = a lot of bread
• molta aigua = a lot of water
• molts llibres = many books
• moltes culleres = many spoons

So in molt gran, no agreement is needed.

Because in Catalan, adjectives are often placed after the noun.

So:

• la cullera petita = the small spoon
• el plat gran = the big plate

In your sentence, the adjectives come after és, because they are acting as part of the predicate:

• La cullera és petita.
• El plat és molt gran.

This is similar to English The spoon is small, where small also comes after the verb.

More generally:

• attributive position: after the noun is common
  
  • una casa gran
• predicative position: after ser/estar/sembla, etc.
  
  • La casa és gran

Yes, in this sentence the word order is very similar to English:

• La cullera = the spoon
• és = is
• petita = small
• però = but
• el plat = the plate
• és = is
• molt gran = very big

So the structure is:

• subject + verb + adjective, però + subject + verb + adverb + adjective

That makes this a very beginner-friendly sentence, because the syntax is close to English.

Yes. Catalan often does not need subject pronouns when the subject is already clear.

In English, you must say:

• It is small.

But in Catalan, the subject can often be omitted if the context is clear:

• És petita. = It is small.
• És molt gran. = It is very big.

In your sentence, the subjects are explicitly stated:

• La cullera
• el plat

So there is no need for an extra pronoun.

A helpful approximate pronunciation is:

• cullera ≈ koo-YE-ra or koo-LYE-ra, depending on accent

The important part for learners is ll.

In Catalan, ll is traditionally a sound like the lli in million for many English speakers, though in some modern accents it may sound closer to y.

So cullera is not pronounced like English kullera with a plain l. The ll is a special Catalan consonant.

Also:

• the stress is on -le- / -lle-
• the final a is a short unstressed vowel

Exact pronunciation varies a bit by dialect, but recognizing ll as a special sound is the key point.

A simple learner-friendly guide:

• plat ≈ plaht
• és ≈ ess
• però ≈ pe-RO or puh-RO, with the stress on the last syllable

A few notes:

• plat ends in a clear t
• és is short and stressed
• però has stress on -rò, which is one reason the accent is important

Pronunciation varies somewhat across Catalan-speaking regions, but these approximations are good enough for a beginner.

Because Catalan often uses the definite article when referring to a specific object, just like English uses the.

So:

• la cullera = the spoon
• el plat = the plate

Without the article, the sentence would sound different and usually less natural in this context.

Since the sentence is talking about a particular spoon and a particular plate, the definite articles are the normal choice.

Sometimes, yes, but context decides.

In your sentence:

• petita clearly means small
• gran clearly means big / large

But in other contexts, gran can also mean grown-up, old, or older depending on the situation.

Examples:

• un nen petit = a small child / a young child
• un nen gran = an older child / a big child
• una casa gran = a big house

So the same adjective can have slightly different meanings depending on what noun it describes.

It would be:

• Les culleres són petites, però els plats són molt grans.

Here is what changed:

• la → les
• el → els
• és → són
• petita → petites
• gran → grans

This shows two important Catalan patterns:

1. Articles change for plural.
2. Adjectives usually agree in number with the noun.

So the singular/plural relationship is very visible in Catalan.