Sin, sitt and sina are used to denote that the "thing" being talked about belongs to the subject.
Sin is used for common (en) words, sitt for neuter (ett) words and sina for plurals.
These are only used for pronouns in the third person.
A neuter word is one that uses the word "ett" in singular indefinite form (Ett äpple). A common word is one that uses the word "en" in singular indefinite form (En klänning).
These are practically reflexive possessive pronouns used in the third person (singular and plural).
I don't understand this. What do you mean by ett and en? Do you just have to memorize what words are ett and en? And is it the noun that would be ett or en?
So are "sitt" "sin" and "sina" gender neutral? Like they could be used to refer to a female or a male?
If you use "sin, sitt, sina", you are referring back to the subject of the sentence (he).
Hon äter sitt äpple, for example, means "She eats her apple" (her own apple). It can never mean "She eats his apple" because that would imply "she" is a "he" at the same time. With current LGBTQ trends, maybe that sentence will be valid in the future. :)
Whenever R is followed by an S, it creates this so-called retroflex sound – even over word borders. (exceptions: when the R is dropped altogether or for speakers who don't have the standard Swedish R). So yes, the R in äter is supposed to merge with the S i sitt here.
Those mean 'his' and 'hers' when things are not owned by the subject of the sentence. So if Han äter sitt äpple, the apple is his own, but Han äter hans äpple, the apple belongs to some other male.
Im always confused by what is meant by en and ett words? Is this like "a" and "an" in english? Or am i way off?
Very much so. However, in English we have the rule "if the word begins with a vowel, then it is an "AN" word. Otherwise we use A for consonants." Example: an apple, a dog, an egg, a fox, etc. In Swedish however there is no rule for which words are EN and which are ETT, so you simply must learn which each word is as you learn each noun. Around 77% of all Swedish words are EN words, so it is safest to use EN when you don't know which is which until told otherwise.
Can someone explain in detail what the difference is between Sitt and Sin? I cannot find a pattern.
As Prague541 has already explained, there is unfortunately no real rule other than that -en words are more common. You just have to learn on a case-by-case basis.
What can't "his own apple" be correct. That as direct and straightforward an answer as anything else.