Language Structure: every language sits inside a defined structure with its own agreed upon rules. The complexity and singularity of this framework directly correlates to the difficulty of translation.
A simple sentence in English has a subject, verb, and object — in that order. For example, “she eats pizza.” But not every language shares this structure. Farsi typically follows a sequence of subject, then object, then verb. And in Arabic, subject pronouns actually become part of the verb itself.
Idiomatic and expressions: the meaning of these peculiar phrases cannot be predicted by the literal definitions of the words it contains. Linguistic professionals insist that idioms are the most difficult items to translate. In fact, idioms are routinely cited as a problem machine translation engines will never fully solve.
Compound words: they are formed by combining two or more words together, but the overall meaning of the compound word may not reflect the meaning of its component words. It’s usually best to think of them in terms of three separate groups. The first group of compound words mean exactly what they say. “Airport,” “crosswalk,” and “seashore,” are all familiar examples.The second group of compound words mean only half of what they say — at least in a literal sense. While a “bookworm” may enjoy burrowing into a good story, these avid readers don’t suddenly become an invertebrate species in the process.
Sarcasm: it frequently loses its meaning when translated word-for-word into another language and can often cause unfortunate misunderstandings. Ideally, a publisher would remove sarcasm from the source text prior to translation. But in cases where that style is central to the content requirements, the publisher should explicitly underscore sarcastic passages. That way, translators will have a chance to avoid literal misunderstandings and suggest a local idiom that may work better in the target language.