illness – enfermedad
To remember that illness is pronounced ehn-fehr-meh-dad (enfermedad) in Spanish, use the following mnemonic:
His father was suffering from a serious illness. He said: 'It's unfair me dad (enfermedad) has to suffer like this'.
Enfermedad is feminine, so it's la enfermedad. Imagine a lady who comes up with a cure for a serious illness: