Considerable describes size or importance, as in a considerable amount of money, while considerate describes a person's thoughtful behaviour towards others. Think of the -ate ending in considerate as short for "thinks of others' state."
The core difference
Considerable measures how much or how significant something is; considerate describes kindness towards other people.
- considerable — large enough in size, amount, or degree to matter: She has considerable experience in negotiation.
- considerate — thoughtful about others' feelings and needs: It was considerate of him to call ahead and warn us.
How to tell them apart
Both words come from consider, but they branched in different directions. Considerable kept the idea of something being "worth considering" because of its size or weight, so it now describes amounts, distances, or degrees. Considerate took a more personal turn, describing someone who actively considers other people's feelings before acting.
The mix-up usually happens in writing about people: a considerable gift is a generous one in size or value, while a considerate gift is one chosen with someone's needs in mind. A gift can be both, but the words are doing different jobs.
