Hola! In this case we use "por" when you are saying that during that period of time you were doing that action. And "Hace" is used when you are going to say how much time the situation was before the present. So in that case you can add the "por" in the sentence and is good as well: Esperamos por dos semanas=We waited for two weeks. Another way could be: Esperamos durante dos semanas. Examples of both can be: Estudiamos por cuatro meses en un semestre= We study for four months in a semester. He tenido dolor de estómago por dos días=I've had stomach pain for two days. Cenamos juntos hace un mes=We had dinner together one moth ago. Hace un año vi a tu amigo= One year ago I saw your friend. I hope that this can help you! I'm also a community tutor if you would like to have a conversation practice or class with me! :) Good luck!

esperar = to wait for

Hi Paulina: It's one single statement with no context, that's the reason. And We don't use prepositions if we don't need to. In other words, that statement may be an answer to a prior question. If you read or listen "Esperamos por dos semanas" it is mainly because is part of a sentence. It may belong to the begining of a conversation or a story. I hope it helps as well.

Hi Paulina, Actually, it would be correct to use the verb "esperar" with "por" to express the duration and with the same meaning as "durante". Example: Esperé por (durante) dos horas en la estación de tren. Although the sentence above is correct, it is also very common to use esperar without preposition to express the duration. Example: 1. Esperé dos horas en la estación. 2: Espera un momento, enseguida vuelvo. I hope it was helpful, Rocio

"Por" in that sense is used in some countries of Latin America as a literal translation from english. You´d never say "esperamos por dos semanas" here in Spain. "Hace" means "ago": "two weeks ago-hace dos semanas". You use "por" meaning parts of the day: "por la mañana-in the morning".