Breakdown of Han tappar sin nyckel.
han
he
nyckeln
the key
sin
his/her/its/their own (en-word)
tappa
to drop / to lose
Questions & Answers about Han tappar sin nyckel.
Why use sin here instead of hans?
Because sin is a reflexive pronoun that refers back to the subject of the sentence (Han). It tells us he dropped his own key. If the sentence was Han tappar hans nyckel, it would mean he dropped some other guy's key!
Why is it sin and not sitt or sina?
The form of the possessive pronoun depends on the thing being owned, not the owner. Nyckel (key) is a singular en-word, so we use sin. If he dropped a singular ett-word, like sitt äpple (his apple), we would use sitt. If he dropped multiple keys, we would use the plural form: sina nycklar.
Does tappar mean 'drops' or 'loses'?
It can mean both! The verb tappar literally means to drop something. However, Swedes commonly use it to mean 'lose' in the sense of misplacing a physical object, like a key or a phone.
Why is it nyckel and not nyckeln (the key)?
Whenever you use a possessive word (like sin, min, din, or hans), the noun that comes after it must be in the indefinite form (without the 'the' ending). So it is always sin nyckel, never sin nyckeln.