"Hard" as an adverb means with effort or intensity; "hardly" means almost not, barely.
Adverb. With great effort, force, or intensity. It is the adverb form of the adjective "hard". Goes after the verb.
She works hard every day to support her family.
Ella trabaja duro todos los dias para mantener a su familia.
It was raining hard when we left the office.
Estaba lloviendo fuerte cuando salimos de la oficina.
He hit the ball hard and it went over the wall.
El golpeo la pelota fuerte y paso por encima del muro.
Adverb. Almost not, barely, very little. Has an almost negative meaning. It is NOT the adverb of "hard": it is a completely different word.
She was so tired she could hardly keep her eyes open.
Estaba tan cansada que apenas podia mantener los ojos abiertos.
I hardly ever eat fast food anymore.
Casi nunca como comida rapida ya.
He hardly slept last night. He looks exhausted.
Casi no durmio anoche. Se ve agotado.
Common mistake
Classic error: "I hardly work" when you mean you work a lot. This means the exact opposite: you barely work. Correct for working a lot: "I work hard." Remember: "hardly" is NOT the adverb of "hard". Adding -ly to "hard" completely changes the meaning — unlike most English adverbs where adding -ly keeps the basic sense.
Trick to remember it
The trap: in English almost all adverbs add -ly (quick/quickly, slow/slowly). But "hard" is an exception: "hard" is already the adverb ("work hard") and "hardly" is a different word with the opposite meaning. Others that do the same: "late" (behind schedule) / "lately" (recently), "near" (close) / "nearly" (almost).
Quick rule
Hard (adv) = with effort / intensely. Hardly = almost not / barely.
Did you know?
"Hardly" behaves grammatically like a negative: "I hardly know her" ≈ "I barely know her". That is why it does not combine with "not": "I do not hardly know her" is wrong (double negative). Correct: "I hardly know her." Other adverbs that work as near-negatives: "barely", "scarcely", "seldom", "rarely".
Exercise 1 · Pick the right one
She studies _____ every night. That is why she always gets top grades.
Exercise 2 · Pick the right one
I _____ recognized him. He had changed so much since high school.
Exercise 3 · Form the word
Hard (adv) = with effort / intensely. Hardly = almost not / barely.
Classic error: "I hardly work" when you mean you work a lot. This means the exact opposite: you barely work. Correct for working a lot: "I work hard." Remember: "hardly" is NOT the adverb of "hard". Adding -ly to "hard" completely changes the meaning — unlike most English adverbs where adding -ly keeps the basic sense.
The trap: in English almost all adverbs add -ly (quick/quickly, slow/slowly). But "hard" is an exception: "hard" is already the adverb ("work hard") and "hardly" is a different word with the opposite meaning. Others that do the same: "late" (behind schedule) / "lately" (recently), "near" (close) / "nearly" (almost).
Bryan López
Founder of SpeakUP Academy