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"Ill" is a form of "ill", an adjective which is often translated as "enfermo". "Disease" is a noun which is often translated as "la enfermedad". Learn more about the difference between "disease" and "ill" below.
disease(
dih
-
ziz
)A noun is a word referring to a person, animal, place, thing, feeling, or idea (e.g., man, dog, house).
1. (medicine)
a. la enfermedad (F)
(f) means that a noun is feminine. Spanish nouns have a gender, which is either feminine (like la mujer or la luna) or masculine (like el hombre or el sol).
Obesity is a disease that affects millions of people.La obesidad es una enfermedad que afecta a millones de personas.
b. la afección (F)
(f) means that a noun is feminine. Spanish nouns have a gender, which is either feminine (like la mujer or la luna) or masculine (like el hombre or el sol).
Heart disease is the leading cause of death for both men and women.Las afecciones cardíacas son la causa principal de muerte tanto entre hombres como mujeres.
c. la dolencia (F)
(f) means that a noun is feminine. Spanish nouns have a gender, which is either feminine (like la mujer or la luna) or masculine (like el hombre or el sol).
It is a very serious disease.Se trata de una dolencia muy grave.
a. la enfermedad (F)
(f) means that a noun is feminine. Spanish nouns have a gender, which is either feminine (like la mujer or la luna) or masculine (like el hombre or el sol).
Violence is a social disease and it should be treated as such.La violencia es una enfermedad social y debe ser tratada como tal.
b. el mal (M)
(m) means that a noun is masculine. Spanish nouns have a gender, which is either feminine (like la mujer or la luna) or masculine (like el hombre or el sol).
In my opinion, superficiality is the greatest disease of our time.A mi parecer, la superficialidad es el gran mal de nuestro tiempo.
ill(
ihl
)An adjective is a word that describes a noun (e.g., the big dog).
1. (sick)
b. malo  (colloquial)
He's ill and won't be going to school today.Está malo y no irá a la escuela hoy.
An adverb is a word that describes a verb, an adjective, or other adverbs (e.g., to run quickly, very tired).
3. (poorly)
a. mal 
It is a lack of respect to speak ill of the dead.Es una falta de respeto hablar mal de los difuntos.
4. (scarcely)
a.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
I can ill afford to eat in a restaurant while I'm unemployed.No me puedo dar el lujo de comer en un restaurante mientras estoy sin empleo.
You can ill afford to make another mistake now that you're on probation.Mal puedes permitirte cometer otro error ahora que estás en libertad condicional.
A noun is a word referring to a person, animal, place, thing, feeling, or idea (e.g., man, dog, house).
5. (problem)
a. el mal (M)
(m) means that a noun is masculine. Spanish nouns have a gender, which is either feminine (like la mujer or la luna) or masculine (like el hombre or el sol).
Don't allow the ills of the world to diminish the good you have in your hearts.No permitan que los males del mundo disminuyan el bien que tienen en sus corazones.