Hann neitar hjálpinni.

Neitar is the 3rd person singular present tense of the verb neita.

So:

• að neita = to refuse / to deny
• hann neitar = he refuses / he denies

In this sentence, hann neitar means he refuses.

A few present-tense forms of neita are:

• ég neita = I refuse
• þú neitar = you refuse
• hann/hún/það neitar = he/she/it refuses
• við neitum = we refuse
• þið neitið = you all refuse
• þeir/þær/þau neita = they refuse

Because hjálpinni means the help, while hjálp by itself means help in an indefinite sense.

The ending -inni shows that the noun is:

• singular
• definite (the)
• dative

So:

• hjálp = help
• hjálpinni = the help

Icelandic usually puts the definite article on the end of the noun instead of using a separate word like English the.

Because the verb neita normally takes a dative object.

That is something Icelandic learners often just have to memorize with the verb:

• neita einhverju = refuse something
• neita hjálpinni = refuse the help

Even if an English speaker expects a direct object with no special marking, Icelandic grammar requires the noun after neita to be in the dative.

So this is not random: it is part of how neita works.

Hjálpinni is:

• dative
• singular
• feminine
• definite

The base noun is hjálp (help), which is a feminine noun.

Useful forms:

• hjálp = nominative singular
• hjálp = accusative singular
• hjálp = dative singular (indefinite)
• hjálpar = genitive singular

With the definite article:

• hjálpin = the help (nominative)
• hjálpina = the help (accusative)
• hjálpinni = the help (dative)
• hjálparinnar = of the help (genitive)

Because Icelandic usually uses a suffixed definite article.

Instead of putting a separate word before the noun, Icelandic often attaches the article to the end:

• hestur = horse
• hesturinn = the horse

The same thing is happening here:

• hjálp = help
• hjálpinni = the help

So the idea of the is still there, but it appears as part of the noun.

Grammatically, neita can mean both refuse and deny in different contexts. But with hjálpinni, the most natural meaning is He refuses the help or He declines the help.

English deny the help sounds less natural in this context, so refuse is usually the better translation here.

So:

• Hann neitar hjálpinni. = He refuses the help.

You would normally use hjálp without the definite ending:

• Hann neitar hjálp.

That means He refuses help.

This is a useful contrast:

• Hann neitar hjálp. = He refuses help.
• Hann neitar hjálpinni. = He refuses the help.

Because of the way this noun declines, the indefinite dative singular happens to look the same as the basic form: hjálp.

Hann neitar hjálpinni is the most neutral, straightforward word order:

• Hann = subject
• neitar = verb
• hjálpinni = object

Icelandic does allow different word orders for emphasis, but the normal version is the one you see here.

For example, a more marked version could be:

• Hjálpinni neitar hann.

That puts extra emphasis on the help. But for everyday neutral usage, Hann neitar hjálpinni is the best pattern to learn first.

Normally, yes, you include hann.

Icelandic usually does not drop subject pronouns as freely as some languages do. So a full sentence normally keeps the subject:

• Hann neitar hjálpinni. = He refuses the help.

You might omit the pronoun only in special contexts, such as very informal speech, notes, or when the structure is otherwise different. But as a standard sentence, keeping hann is correct and natural.

Yes. Icelandic present tense often covers both the English simple present and present continuous, depending on context.

So Hann neitar hjálpinni can mean:

• He refuses the help
• He is refusing the help

In many cases, English chooses between those two based on the situation, while Icelandic simply uses the present tense form neitar.