What does "no puedo" mean?
"No puedo" simply means "I can't" or "I am unable to." It comes from the verb poder (to be able to). Use it to express a lack of ability, a lack of permission, or an impossibility in a given moment.
Examples
1. Lo siento, hoy no puedo ir a la fiesta.
I'm sorry, I can't go to the party today. (presente de indicativo)
2. De niño, no podía comer dulces antes de la cena.
As a child, I couldn't eat sweets before dinner. (imperfecto de indicativo)
3. Ayer no pude terminar el informe a tiempo.
Yesterday I couldn't finish the report on time. (pretérito)
4. No podré viajar el próximo mes por el trabajo.
I won't be able to travel next month because of work. (futuro)
5. Sin tu ayuda, no podría resolver este problema.
Without your help, I couldn't solve this problem. (potencial simple)
6. Es una lástima que no pueda acompañarte.
It's a pity that I can't (or he/she can't) accompany you. (presente de subjuntivo)
7. Si no pudiera caminar, me sentiría muy frustrado.
If I couldn't walk, I would feel very frustrated. (imperfecto de subjuntivo)
8. No he podido dormir bien estas últimas noches.
I haven't been able to sleep well these last few nights. (perfecto de indicativo)
9. Antes de la operación, no había podido hacer deporte.
Before the surgery, I hadn't been able to do sports. (pluscuamperfecto)
10. Apenas no hubo podido entrar, se marchó a casa.
As soon as he hadn't been able to enter, he went home. (pretérito anterior)
11. Para mañana, no habré podido leer todo el contrato.
By tomorrow, I won't have been able to read the whole contract. (futuro perfecto)
12. No habría podido ganar la carrera sin mi entrenador.
I wouldn't have been able to win the race without my coach. (potencial compuesto)
13. No creo que ella no haya podido recibir el paquete.
I don't think she hasn't been able to receive the package. (perfecto de subjuntivo)
14. Si no hubiera podido escapar, ahora estaría en la cárcel.
If he hadn't been able to escape, he would be in jail now. (pluscuamperfecto de subjuntivo)
15. ¡No digas que no puedes, inténtalo de nuevo!
Don't say you can't, try it again! (imperativo context)