Generate a topic word for the given sentence. A topic word is usually the name of a person, place, animal, concept or object the sentence is focusing on.
--------
Question: causality is a way to describe how different events relate to one another.

Answer: causality


Question: the northumbrian smallpipes are a type of bagpipes from north east england.

Answer: northumbrian smallpipes


Question: the horst-wessel-lied ("horst wessel song"), also known as "die fahne hoch" ("the flag on high", from its opening line), was the anthem of the nazi party from 1930 to 1945.

Answer:
horst-wessel-lied