unzertrennlich
inseparable
Describes people who have a very close relationship and are almost always together.
Seit dem Kindergarten sind die beiden Freundinnen unzertrennlich.
The two friends have been inseparable since kindergarten.

inseparable
Loading your saved state.
inseparable
Describes people who have a very close relationship and are almost always together.
Seit dem Kindergarten sind die beiden Freundinnen unzertrennlich.
The two friends have been inseparable since kindergarten.

The word is made up of several parts: the prefix 'un-' negates the adjective 'zertrennlich' (separable). 'Zertrennlich' in turn comes from the verb 'trennen' (to separate) with the prefix 'zer-' (apart). Literally, it therefore means 'not able to be separated apart'.
Die beiden Schwestern sind einfach unzertrennlich.
The two sisters are simply inseparable.
When referring to people, 'unzertrennlich' (inseparable) is almost always used to describe a very close friendship or partnership. Typical combinations are 'unzertrennliche Freunde' (inseparable friends) or 'ein unzertrennliches Paar' (an inseparable couple).
Seit ihrer Kindheit gelten sie als unzertrennliche Freundinnen.
Since childhood, they have been considered inseparable friends.
For abstract ideas, 'unzertrennlich' (inseparable) is often combined with the phrases 'miteinander verbunden' (connected to each other) or 'zusammengehören' (to belong together). It emphasizes that two concepts cannot be considered in isolation from each other.
Für den Philosophen waren Freiheit und Verantwortung unzertrennlich miteinander verbunden.
For the philosopher, freedom and responsibility were inseparably linked.
narrow / close / tight
'eng' and 'unzertrennlich' can both describe strong closeness between people. 'eng' is more general: 'eine enge Freundschaft' (a close friendship) means that people know and trust each other well. 'unzertrennlich' is stronger and more figurative. It describes people who are almost always together and are hardly ever seen without each other. The words can be confused because both express closeness. But 'unzertrennlich' only fits when the relationship seems especially strong and the people do a lot together.

Die beiden Kinder sind unzertrennlich und spielen jeden Nachmittag zusammen.
The two children are inseparable and play together every afternoon.
Du hast zu deinem alten Schulfreund noch immer einen engen Kontakt.
You still have close contact with your old school friend.