"Considerable" means "a lot" or "not a small amount". Here are some examples:

There was considerable damage to the apartment when they moved out: scratches on the floor, stains on the walls, broken cabinet hinges, and so on.

We flew them in at considerable expense.

You could save a considerable amount of money by doing it yourself.

"Considerable" is a somewhat formal word. You can use it in business situations, in essays, in speeches, and so on.

The words that most commonly follow "considerable" are:

• a considerable amount
• a considerable number
• considerable attention
• considerable evidence