A deductive argument is one that starts with general premises and moves to specific conclusion. It is generally formed by positing that something true of a class must be true of all individuals belonging to the class. Deductive arguments can be syllogisms, based on premisses that are universally true and operating by rigorous deduction, or enthymemes, which are based on premisses that are probable or signs. A typical syllogism would be:

All dogs are quadrupeds.
Lassie is a dog.
Therefore Lassie is a quadruped.

An enthymeme is similar in form but is based on probable rather than certain premisses:

Most small dogs bark a lot.
Yippy is a small dog.
Therefore Yippy barks a lot.