As a Noun:
1. A strong desire and interest in doing something. English = keenness, eagerness, enthusiasm.
As a Verb or Adjective:
1. To want to do something very much. English = (be) keen, (be) eager.
2. To be enthusiastic and interested in what you are doing or will do. English = (be) keen, (be) eager.
3. To have interest in something. English = (be) interested in.
4. To have no objection to doing something you have been asked to do. Idiomatic English = (be) glad to do something, (be) happy to do something.