Contestar vs. descolgar
The Spanish verbs 'contestar' and 'descolgar' are commonly used in relation to telecommunication, often being translated to English as 'to answer'. However, these words are not synonymous; they have different contexts and uses.
Contestar
This verb is used in the sense of 'to answer' or 'to respond', and it refers to the action of replying to a question, comment, or action. It can be used in many contexts, not just in relation to answering a phone.
Voy a contestar las preguntas del profesor.
(I am going to answer the professor's questions.)
No has contestado mi email.
(You have not answered my email.)
¿Por qué no contestas cuando te llamo?
(Why don't you answer when I call you?)
Descolgar
This verb means 'to pick up' or 'to unhook', but it is primarily used in the context of answering telephones. It refers specifically to the physical action of picking up a phone or taking it off its hanging place (which was more literal in older, wall-mounted phones).
Descolgué el teléfono y no había nadie en la línea.
(I picked up the phone and there was no one on the line.)
Debes descolgar rápido cuando suena el teléfono en una empresa.
(You must pick up quickly when the phone rings in a business.)
Ella descolgó el auricular y comenzó a marcar.
(She picked up the receiver and began dialing.)
Summary
'Contestar' and 'descolgar' both share connections with telecommunications, but cannot be used interchangeably. While 'contestar' pertains broadly to answering or responding (a call, a question etc), 'descolgar' is specific to the physical act of picking up a telephone receiver.