How do treaties and pacts differ?

Question

Definition of treaty by Cambridge Dictionary Online:

a written agreement between two or more countries, formally approved and signed by their leaders

Definition of pact by Cambridge Dictionary Online:

a formal agreement between two people or groups of people

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So should I call it a Non-aggression Treaty or Non-aggression Pact? They seem to be the same for me when is used.

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Some sources on the Internet suggest that a treaty is between countries while a pact is between alliances.

e.g. Nazi-Soviet Pact

Source: https://answers.yahoo.com/question/index?qid=20090510153115AABqJ4A

However, I find that it is inaccurate because the Cambridge Dictionary Online gives this example sentence:

The United States and Canada have signed a free-trade pact.

Source: http://dictionary.cambridge.org/dictionary/english/pact

I also remembered there is a source that says Non-aggression Pact is to end current wars while Non-aggression Treaty is just an agreement.

Answer 1

There are no exact synonyms expect where stipulated (say in the sciences).

But treaty and pact are vague enough and overlap in meaning enough that they can easily be swapped in many contexts.

Did I mention that dictionaries aren't perfect either. That is constraint of dictionary writing, one may have limits on the length of a definition and nuances one can state (even the OED has some constraints, though fewer than most).

A treaty is an agreement between nations, either enemies or allies. It is written and authorized and ratified by both/all sides. Sometimes for variation, it might be nice to call this a pact between the nations.

A pact is a little more loose. I can make a pact with a friend of mine to always meet on New Years Day. But to call that a treaty would be wrong. If I made a similar arrangement with a person who is not my friend, say the owner of a competing business to informally discuss avoiding encroaching on the others business, that might be metaphorically called a treaty, but pact would work better.

Answer 2

Agreements

Treaties are also pacts, and sometimes vice versa. Both are agreements.

Although both pacts and treaties are types of agreements, they are not separate, distinct types of agreement with no overlap.

Rather than being different things, substantial overlap occurs between pact and treaty, so there can be no right answer to your question about which one you “should” use.

• A pact is merely an agreement between persons or parties, whether formal or informal. The word is often used loosely not specifically. The OED provides:

  An agreement between persons or parties, a compact.

• A treaty is specifically a signed contract between states with force of law behind it. The OED offers:

  3b. spec. A contract between two or more states, relating to peace, truce, alliance, commerce, or other international relation; also, the document embodying such contract, in modern usage formally signed by plenipotentiaries appointed by the government of each state. (Now the prevailing sense.)

You’ll also find the related terms accord, concord, understanding, arrangement, understanding, charter, compact, convention, covenant, settlement used to describe agreements.

Again, do not think that these are all somehow different things applicable to only one situation each. Language is not math nor even computer programming, and it just does not work that way.

Treaties in Domestic Law versus International Law

You also need to consider how these terms are used in different sectors of the anglosphere. For example, the Wikipedia article on the Treaty Clause of the American Constitution explicitly points this out in the following text:

In the United States, the term "treaty" is used in a more restricted legal sense than in international law. U.S. law distinguishes what it calls treaties from congressional-executive agreements and sole-executive agreements. All three classes are considered treaties under international law; they are distinct only from the perspective of internal United States law. Distinctions among the three concern their method of ratification: by two-thirds of the Senate, by normal legislative process, or by the President alone, respectively. The Treaty Clause empowers the President to make or enter into treaties with the "advice and consent" of two-thirds of the Senate. In contrast, normal legislation becomes law after approval by simple majorities in both the Senate and the House of Representatives.

Throughout U.S. history, the President has also made international "agreements" through congressional-executive agreements (CEAs) that are ratified with only a majority from both houses of Congress, or sole-executive agreements made by the President alone.

Therefore if you are talking about formal agreements between the United States and other plenipotentiaries, be sensitive to what treaty means in that context.