chain
In German, the word for chain is 'Kette'. It is a noun and is used in the same way as in English, referring to a series of interconnected links or rings. It can be used to describe a physical chain, or metaphorically to describe a series of events or a chain of command.
The chain is very long.
In this context, 'Kette' translates to 'chain'. The speaker is observing and commenting on the length of the chain. Note that 'Kette' can refer to a chain in general, not just a necklace.
The chain of my bike has torn.
This sentence describes a situation where the speaker's bicycle chain has broken, with 'Kette' referring to a bicycle chain. Note the use of 'meines Fahrrads', which translates to 'of my bicycle', to specify ownership of the chain.