1. The idea of through, around or by (direction of motion)

• Paso por el parque. I go through the park.

An indefinite or general direction physically

• Por el norte, sur, este, oeste. Around/toward/in the direction of the north, south, east, west.

or through time

• Por la mañana, tarde, noche: in (during) the morning, afternoon, evening.

2. Cause or reason prompting a situation (initiating motion)

• Él lucha por la libertad. He fights for freedom.

  Mi mamá pasa por nosotros. My mother is picking us up.

  Vengo por ti. I'm coming for you.

Impersonal expressions expressing initiating motion or prompts

• Por favor, por fin, por eso, por lo general, por lo menos: Please (as a favor), finally (in the end), that's why/so, in general, at least.

Responsibility of action (initiating motion)

• Es escrito por Jorge Luís Borge. It's written by Jorge Luis Borges.

  Es arrestado por la policía. He is arrested by the police.

3. Direction of motion

Exchange

• José compra una botella de vino por $300. José buys a bottle of wine for $300.
  

Substitution

• José trabaja por mí. José is working for me (in my place, because I am ill or on vacation)

Substitution/Error in identity

• Tomé a ella por la ratona. I mistook her for the shoplifter.

4. Total time of an action

Duration of time/motion

• Voy a Cuba por 3 años. I'm going to Cuba for 3 years.

Frequency (motion of time)

• Estudiamos español dos días por semana. We study Spanish 2 days a (per) week.

5. Units of measure (mode of motion)

• por libra, por yarda etc... by the pound, by the yard etc...

Relations, proportions, dimensions

• 3 x 4 = 3 por 4. 100% = 100 por ciento.

Measurement (incl. time) still to go to reach a goal

• Tengo tres páginas por leer. I have three pages to go/ left to read.

  Estamos por salir. We're about to head out.

6. Mode of transport or communication

• por avión [by plane], por Fax [by Fax], por teléfono [by phone], por Delta, por Greyhound Bus