"Interested" describes the subject who feels the interest; "interesting" describes the object that causes it.
Adjective. Feeling interest in something. Describes the person (or subject) experiencing the emotion. Always followed by "in".
She is interested in learning Japanese.
A ella le interesa aprender japones.
Are you interested in coming to the event?
¿Te interesa venir al evento?
He was not interested in the job offer.
No le intereso la oferta de trabajo.
Adjective. That awakens interest or curiosity. Describes the thing, person, or event that produces that feeling in others.
The documentary was very interesting. I learned a lot.
El documental fue muy interesante. Aprendi mucho.
She has an interesting perspective on the topic.
Ella tiene una perspectiva interesante sobre el tema.
What an interesting question! I have never thought about that.
¡Que pregunta tan interesante! Nunca habia pensado en eso.
Common mistake
Very common error: "The class was interested" when you mean the class was engaging. Correct: "The class was interesting." The class does not feel interest — it causes interest. Another error: "I am very interesting in history." Correct: "I am very interested in history." You feel the interest, so you are "interested in", not "interesting in".
Trick to remember it
Ask: who or what experiences the emotion? That person or thing uses "-ed". Who or what causes it? That one uses "-ing". I (subject) experience it = I am interested. The movie (object) causes it = The movie is interesting. This pattern applies to dozens of adjectives: bored/boring, excited/exciting, confused/confusing, tired/tiring.
Quick rule
Interested = the subject feels the emotion (person). Interesting = the object causes the emotion (thing or event).
Did you know?
This -ed/-ing pattern exists in more than 30 adjective pairs: amazed/amazing, shocked/shocking, bored/boring, excited/exciting, frustrated/frustrating, exhausted/exhausting, satisfied/satisfying. All work the same: -ed for who feels it, -ing for what causes it. Learn the pattern and you master them all at once.
Exercise 1 · Pick the right one
The lecture about ancient civilizations was really _____. I did not want it to end.
Exercise 2 · Pick the right one
She is very _____ in marine biology. She wants to study it at university.
Exercise 3 · Form the word
Interested = the subject feels the emotion (person). Interesting = the object causes the emotion (thing or event).
Very common error: "The class was interested" when you mean the class was engaging. Correct: "The class was interesting." The class does not feel interest — it causes interest. Another error: "I am very interesting in history." Correct: "I am very interested in history." You feel the interest, so you are "interested in", not "interesting in".
Ask: who or what experiences the emotion? That person or thing uses "-ed". Who or what causes it? That one uses "-ing". I (subject) experience it = I am interested. The movie (object) causes it = The movie is interesting. This pattern applies to dozens of adjectives: bored/boring, excited/exciting, confused/confusing, tired/tiring.
Bryan López
Founder of SpeakUP Academy