Peninsula
Part of speech: noun
Definition: A piece of land projecting into water from a larger land mass.
Example sentence: Since the Korean War, U.S. and South Korea have established an enduring friendship with shared interests, such as denuclearizing the Korean Peninsula, combating aggression abroad and developing our economies.
Peninsular
Part of speech: adjective
Definition: Of, pertaining to, resembling, or connected with a peninsula.