Colony. Province can be stretched to fit- implying a subordinate Tug-Barge state with the Mainland. That is a Province is remotely ruled.
A territory under the control of another country is called a colony.
It is called ceding or transferring territory.
An area owned by another country is called a territory or colony. It is governed and administered by the owning country, often maintaining political and economic ties to the colonizing nation.
a colony (of the country that rules it)
Commonwealth
It is called annexation when one country takes over another country and incorporates it into its own territory without the consent of the other country.
territory
A small country inside another country is typically referred to as an enclave. This means that the smaller country is surrounded by the territory of the larger country.
A territory ruled by another nation usually very far away is called a colony. This type of governance often involves control over political, economic, and social aspects of the territory by the ruling nation.
That can be classified as an annexation or an invasion or both.
Generally, "constituent country" is a term applied to territories that call themselves countries, that are a part of a bigger sovereign country. For example, England is a constituent country of the United Kingdom and Greenland is a constituent country of the Kingdom of Denmark. If you mean a sovereign country within another sovereign country, that is called an enclave.
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