Questions & Answers about Onko ne kateellisia meiän uudesta kämpästä?
Why is it meiän instead of meidän?
This matches our current lesson on spoken Finnish (puhekieli). The "d" between vowels is very often dropped in speech, so meidän (our) shrinks to meiän. You will hear this all the time with words like teidän (teiän) and verbs like lähden (lähen).
Why does the sentence use onko ne instead of ovatko he?
In spoken Finnish, people almost always use ne (literally "those") instead of he for "they". Crucially, spoken Finnish pairs ne with the singular verb form instead of the plural. So, he ovat becomes ne on, which turns the question form into onko ne.
Why is kateellisia in the partitive plural form?
Because it is an adjective describing a plural subject (ne). In Finnish, when a subject is plural, the descriptive adjective (the predicative) must be in the partitive plural. If the subject were singular, you would use the basic nominative form: Onko hän kateellinen?
Why is "our new flat" put in the elative case (uudesta kämpästä)?
The adjective kateellinen (jealous) requires the thing you are jealous of to be in the elative case (-sta/-stä). This is its "rection". While English uses the preposition "of", Finnish expresses this relationship by attaching the case ending to both the noun and its modifying adjective.