"Answer" responds to a question or call; "reply" responds to a message, letter, or comment.
To give a response to a question. To pick up the phone or door. Broader in use.
Can someone answer the door? I have my hands full.
¿Puede alguien abrir la puerta? Tengo las manos ocupadas.
She did not answer my question. She changed the subject.
Ella no respondio mi pregunta. Cambio el tema.
I called three times but he did not answer.
Llame tres veces pero el no contesto.
To respond to a written message, email, letter, comment, or in formal conversation.
I have not had time to reply to her email yet.
Todavia no he tenido tiempo de responder su email.
He replied with a one-word message: "No."
El respondio con un mensaje de una palabra: "No."
Please reply to this invitation by Friday.
Por favor responde esta invitacion para el viernes.
Common mistake
Using "answer" for written messages where "reply" is more natural: "I answered his email" works but "I replied to his email" is more idiomatic. The reverse: "reply the phone" does not exist — it is always "answer the phone". And "reply the door" is not English. Phones and doors are only "answered".
Trick to remember it
Preposition rule: "reply" almost always needs "to" when it has an object — "reply TO the email", "reply TO his comment". "Answer" is direct — "answer the question", "answer the phone" (no "to"). If you need to put "to" before the object, it is probably "reply".
Quick rule
Answer = respond to question / phone / door (direct). Reply = respond to message / email / letter (+ to).
Did you know?
In email software, the buttons "Reply" and "Reply All" are universal in English. The button never says "Answer" in that context. But the out-of-office automatic response is called "Out of Office reply" or "Auto-reply" — not "Auto-answer". Emails have their own dedicated words.
Exercise 1 · Pick the right one
I sent the proposal three days ago and they have not _____ yet.
Exercise 2 · Pick the right one
Could someone please _____ the phone? I am in the middle of a meeting.
Exercise 3 · Form the word
Answer = respond to question / phone / door (direct). Reply = respond to message / email / letter (+ to).
Using "answer" for written messages where "reply" is more natural: "I answered his email" works but "I replied to his email" is more idiomatic. The reverse: "reply the phone" does not exist — it is always "answer the phone". And "reply the door" is not English. Phones and doors are only "answered".
Preposition rule: "reply" almost always needs "to" when it has an object — "reply TO the email", "reply TO his comment". "Answer" is direct — "answer the question", "answer the phone" (no "to"). If you need to put "to" before the object, it is probably "reply".
Bryan López
Founder of SpeakUP Academy