Fortification (noun)

1. The action of fortifying or the state of being fortified, especially the strengthening of a place or position against attack.
2. Something that fortifies, such as a wall or rampart, a fortified building or castle, or a military line of defense.
3. The addition of vitamins, minerals, or other nutrients to food or drink.

Origin:

Late middle english: from old french fortification, from fortifier "strengthen", from latin fortificare.

Examples:

1. The city was surrounded by walls and fortifications to protect it from invaders.
2. The fortifications at the castle were built to withstand the most powerful cannons of the time.
3. The soldiers set up a line of fortifications to protect their position.
4. Fortification of foods with vitamins and minerals has become common practice.
5. The fortification of the city walls helped ensure its survival during the siege.