Kua spiser gress.

Because kua is the definite singular form: the cow.

The basic noun is ku = cow.
In Bokmål, a feminine noun like ku can be:

• ei ku = a cow
• kua = the cow

So in Kua spiser gress, the subject is a specific cow: the cow.

In Norwegian, the definite article is usually attached to the end of the noun.

So instead of a separate word like English the cow, Norwegian often uses:

• kua = the cow
• bilen = the car
• huset = the house

This is one of the first big differences English speakers notice.

Yes, ku is traditionally a feminine noun.

In Bokmål, many feminine nouns can either:

• keep their feminine forms: ei ku / kua
• or use common-gender forms: en ku / kuen

So kua and kuen can both occur in Bokmål, but kua is very common and natural.

If you are learning standard Norwegian, kua is absolutely normal and worth learning.

Spiser is the present tense of å spise = to eat.

So:

• å spise = to eat
• spiser = eat / eats / is eating, depending on context

Norwegian verbs do not change for person:

• jeg spiser = I eat
• du spiser = you eat
• kua spiser = the cow eats
• vi spiser = we eat

That makes Norwegian verb conjugation simpler than English.

Because gress here is being used as a mass noun in a general sense, like English grass.

So:

• Kua spiser gress = The cow eats grass.

You do not need an article when talking about the substance in general.

If you wanted to refer to a specific patch or instance of grass, you might use the definite form:

• Kua spiser gresset = The cow is eating the grass

So the sentence with bare gress sounds general and natural.

It is the basic subject–verb–object order:

• Kua = subject
• spiser = verb
• gress = object

So the structure is:

The cow + eats + grass

That is the most straightforward word order in a simple Norwegian main clause.

Yes, but Norwegian main clauses follow the V2 rule: the finite verb usually stays in second position.

For example:

• Kua spiser gress.
• I dag spiser kua gress. = Today, the cow eats grass.

Notice that when I dag comes first, spiser still stays second, and kua moves after the verb.

This is an important pattern in Norwegian.

Yes.

The Norwegian present tense often covers both:

• habitual meaning: The cow eats grass
• ongoing meaning: The cow is eating grass

Context usually tells you which one is meant.

If you want to be more explicitly progressive, Norwegian can also use expressions like:

• Kua står og spiser gress = The cow is standing there eating grass

But the simple present is often enough.

Gress is normally a neuter noun:

• et gress = a grass / a kind of grass
• gresset = the grass

But in everyday use, it is very often treated as an uncountable mass noun, so learners most often meet it without an article:

• spise gress
• klippe gress
• det er mye gress her

So in this sentence, you should think of gress as grass in the general material sense.

You would normally say:

• Ei ku spiser gress

In Bokmål you may also see:

• En ku spiser gress

So the contrast is:

• Ei ku / en ku = a cow
• Kua / kuen = the cow

That is the key difference between indefinite and definite forms here.