Both mean "not easy", but "hard" also means physically firm or working intensely.
Requiring effort or not easy. Also: physically firm, or with great intensity (as adverb).
The exam was really hard. I almost failed.
El examen fue muy dificil. Casi reprobe.
She works hard every day to support her family.
Ella trabaja duro todos los dias para mantener a su familia.
This bed is too hard. I cannot sleep on it.
Esta cama es muy dura. No puedo dormir en ella.
Requiring skill, effort, or being complex to understand or accomplish.
This grammar rule is very difficult to explain.
Esta regla gramatical es muy dificil de explicar.
It was a difficult decision to make under pressure.
Fue una decision dificil de tomar bajo presion.
Learning a new language as an adult can be difficult.
Aprender un nuevo idioma de adulto puede ser dificil.
Common mistake
The error almost never happens by substituting "difficult" for "hard" (it usually works). The danger is the opposite direction with the adverb: "She works hardly" is WRONG and means something completely different. "Hardly" = barely/almost not. "Hard" (without -ly) = with intensity. "She works hard" = works with intensity. "She hardly works" = barely works at all.
Trick to remember it
The unique danger of "hard": as an adverb, "hard" does NOT add -ly. "Work hard, study hard, try hard, rain hard" — all correct. "Hardly" exists but means "barely". This rule is the opposite of almost every adverb in English.
Quick rule
Hard and difficult = not easy (interchangeable in that sense). Hard as adverb = intensely (NOT hardly). Hard physical = firm/solid.
Did you know?
"Difficult" comes from Latin "difficilis" (not easy). "Hard" comes from Proto-Germanic "harduz" (strong, solid). That is why "hard" has the physical meaning of firmness in addition to the abstract sense of difficulty, while "difficult" only has the abstract meaning. This duality creates the adverb trap.
Exercise 1 · Pick the right one
She studied _____ for the exam and was confident going in.
Exercise 2 · Pick the right one
The instructions were very _____ to follow. We needed help.
Exercise 3 · Form the word
Hard and difficult = not easy (interchangeable in that sense). Hard as adverb = intensely (NOT hardly). Hard physical = firm/solid.
The error almost never happens by substituting "difficult" for "hard" (it usually works). The danger is the opposite direction with the adverb: "She works hardly" is WRONG and means something completely different. "Hardly" = barely/almost not. "Hard" (without -ly) = with intensity. "She works hard" = works with intensity. "She hardly works" = barely works at all.
The unique danger of "hard": as an adverb, "hard" does NOT add -ly. "Work hard, study hard, try hard, rain hard" — all correct. "Hardly" exists but means "barely". This rule is the opposite of almost every adverb in English.
Bryan López
Founder of SpeakUP Academy