TASK DEFINITION: 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.
PROBLEM: cornish people (cornish: kernowyon) are often regarded as a distinct ethnic group or national identity of the united kingdom, originating in cornwall.

SOLUTION: cornish people

PROBLEM: euclid's lemma, also called euclid's division lemma or euclid's first theorem, is an important lemma.

SOLUTION: euclid's lemma

PROBLEM: metlink is the marketing name for all public transport operators' in melbourne, australia.

SOLUTION:
metlink