والجزء الذي تكرر بينهما يسمى حدا أوسط.
The term repeated between the two premises is called the middle term.
Example:
Zayd is human.
Every human is an animal.
Therefore Zayd is an animal.
Human is the middle term. It is linked to Zayd in the minor premise and to animal in the major, but does not occur in the conclusion. It supplies the bridge between the other terms.