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"Interested" describes the subject who feels the interest; "interesting" describes the object that causes it.
Side-by-side comparison
"Interested" describes the person who feels curiosity or interest. The person is the subject experiencing the feeling. It is always followed by "in".
She is interested in learning Japanese.
Are you interested in coming to the event?
He was not interested in the job offer.
"Interesting" describes the thing, person, or event that causes that curiosity or interest in others. "An interesting book" = a book that makes readers feel interested.
The documentary was very interesting. I learned a lot.
She has an interesting perspective on the topic.
What an interesting question! I have never thought about that.
Common mistake
- •"The class was interested" when meaning it was engaging is wrong: the class causes interest, it does not feel it.
- •"The class was interesting." You feel the interest: "I am interested in history." The movie causes it: "The movie is interesting."
Trick to remember it
- •Who or what experiences the emotion? That person uses "-ed".
- •Who or what causes it? That thing uses "-ing".
- •I feel it = "I am interested".
- •The movie causes it = "The movie is interesting".
Quick rule
- •"-ed" = the subject feels the emotion (person).
- •"-ing" = the object causes the emotion.
- •Applies to: bored/boring, excited/exciting, confused/confusing, tired/tiring.
Did you know?
The -ED / -ING pattern exists in more than 30 pairs of emotional adjectives in English, all following exactly the same logic. Some of the most used: amazed/amazing, shocked/shocking, bored/boring, excited/exciting, frustrated/frustrating, exhausted/exhausting, satisfied/satisfying, disappointed/disappointing, overwhelmed/overwhelming. Once you internalize the rule (person feels → -ED; thing causes → -ING), you master all of them at once without needing to learn them one by one. It is one of the most productive grammatical systems in English, and one of the most underrated in traditional teaching, which treats them as independent vocabulary items rather than as a systematic pattern.
Practise what you learned
Exercise 1 · Pick the right one
That documentary was so _____! I learned so many new things.
Exercise 2 · Pick the right one
She is very _____ in learning to paint. She has just signed up for a class.
Exercise 3 · Form the word
Related word pairs
One describes how you feel, the other describes what causes that feeling.
'Sensible' means practical and reasonable; 'sensitive' means easily affected or hurt, in feelings or physically.
'A' is used before consonant sounds; 'an' is used before vowel sounds.
'A lot of' works for countable and uncountable; 'many' only for countable; 'much' only for uncountable.
Bryan López
Founder of SpeakUP Academy