If ever a creature's toughness is reduced to zero (or less), it will be destroyed as a state-based effect. If a 1/1 creature gets a -1/-1 counter, then effectively it has a toughness of zero, and will be destroyed.

Edit: Note that a creature having 0 toughness is not a destroy effect. As per the state based actions, it will be put into its owner's graveyard. This does trigger "Dying" effects. This is an important distinction as having 0 toughness is one of the ways to get rid of indestructible creatures.

The toughness of a person is sometimes measured by his/her emotions. This is an example of toughness in a sentence.

It depends on the ceramic. Most ceramics have fracture toughness between 0.7 AND 1 MPa - m^1/2. Some are lower, and some higher, up to 5 MPa-m^1/2

it lets you know the toughness of the metal......

The factors affecting toughness of rock includes;

1. Rock Texture.

2. Rock Structure.

3. Weathering activities.

4. Metamorphism.