A quick breakdown:
So the structure is basically:
A very natural gloss is:
Because sjá is the infinitive, meaning to see.
In the sentence, you need the verb form that matches I, so Icelandic uses the 1st person singular present:
Some present-tense forms of sjá are:
So Ég sé is simply the correct conjugated form.
Because hundinn is the form used for the dog when it is the direct object of the verb.
Here, the dog is what is being seen, so it is in the accusative case.
Compare:
A useful comparison:
So the short answer is:
In Icelandic, the is often added to the end of the noun instead of being written as a separate word.
So:
and
This is called the suffixed definite article.
So unlike English:
Because the sentence needs the accusative form, not the nominative form.
For hundur:
Since in Ég sé hundinn, the dog is being seen, it is the object, so hundinn is correct.
This is a very common pattern in Icelandic: the noun changes form depending on its role in the sentence.
Because fyrir aftan takes the accusative case, and the accusative singular definite form of hús is húsið.
For hús:
So after fyrir aftan, Icelandic uses:
A detail that often confuses learners: with many neuter nouns, the nominative and accusative look the same. So even though húsið looks like a basic form, here it is functioning as accusative.
It is best to learn fyrir aftan as a single unit meaning behind.
Even though it has two words, in practice learners should treat it like a set expression or compound preposition.
So memorize:
rather than trying to translate each piece separately every time.
This is common in Icelandic. Some location expressions are made of more than one word but function as one preposition-like phrase.
In this sentence, the most natural reading is that it describes where the dog is:
That is also the most likely interpretation in English for I see the dog behind the house.
Could context make things ambiguous? Sometimes, yes. But as written, the normal understanding is:
This sentence uses a very normal, neutral word order:
So the pattern is basically:
That is a very common order in simple Icelandic main clauses.
Icelandic word order can be more flexible than English, especially for emphasis or style, but this version is the plain, straightforward one a learner should be comfortable with first.
Because in Icelandic, accented vowels are part of the normal spelling system. They are not optional decoration.
For example:
So you should learn the accented forms as part of the word itself:
These accents affect pronunciation and are important in correct spelling.
Yes, but the meaning would change.
Compare:
So the definite endings matter:
Without them, the nouns are indefinite, more like a dog and a house.