Breakdown of Þú þarft að rökstyðja skoðunina þína.
að
to (infinitive marker)
þurfa
to need
þinn
your (m, f, n: þinn, þín, þitt)
skoðunin
the opinion
Questions & Answers about Þú þarft að rökstyðja skoðunina þína.
What does the word rökstyðja literally mean?
Why does skoðun have the definite article ending (-ina) when we are already saying your (þína)?
In Icelandic, when you place a possessive pronoun like þína after a noun, the noun must take the definite article. Since skoðun (opinion) is feminine and in the accusative case here, it becomes skoðunina, followed by the matching pronoun þína.
Could I say þína skoðun instead of skoðunina þína?
Yes, but it changes the emphasis. Placing the pronoun after the noun with the definite article (skoðunina þína) is the neutral, everyday way to express possession. Putting it before the indefinite noun (þína skoðun) heavily emphasizes the word your, as if saying that is YOUR opinion, not mine.
How is þarft að different from verður að in this context?
The verb phrase þarft að comes from þurfa að and means you need to, which fits well for giving strong advice or outlining a requirement. If you used verður að (from verða að), it would mean you must, sounding more like an absolute command.