I'm sitting in the restaurant of a hotel close to the Lima, PerĂº airport, near a glass window separating the non-smoking section from the smoking section. A sign on the wall of the smoking section catches my attention, because it contains one of my grammatical pet peeves. The sign reads: Fumar puede causar severos problemas con la salud…".
Anybody but me bothered by that?
The problem here is that a problem can't be severo – only your mom, your dad, your first grade teacher, a law, or a cop enforcing the law can be severo.
If a problem is bad, or serious, it's grave.
The problem here, in other words, is that the English word severe does not translate to severo, but rather in Spanish is grave. The Spanish word severo means "strict." Grave means "severe," or "serious."
So when you have a bad -- or severe -- disease, you have una enfermedad grave. If you have a serious problem, you have un problema grave.
Another error, probably even more egregious (or grave, if you will), is when someone wants to say "serious problem," so they say "un problema serio." The word serio does indeed mean serious, but in the since of "sober," or "not funny."
Mi amigo Mark es muy serio, porque tiene un problema grave: su esposa es un poco severa con el.