If every word in Spanish had an equivalent in English, Spanish and English would be the same language separated by distinct accents. One word in Spanish that has no English equivalent — or rather, many equivalents — is ya.
The word ya is an adjective to emphasize that the event occurs at a particular time. What time? It can be it the past, present, or future, or ya can express a relationship between one time and another. Ya can be translated as "immediately," "soon," "already," "never," or "finally," among other timely adverbs.
Some examples may make this more clear:
Ya hemos hablado de eso. We've already talked about that.
¿Ya estás aquí otra vez? Are you here again?
Ya podías haberme avisado. You could have told me earlier.
¡Basta ya! Enough already!
¡Ese ya no se casa! He'll never get married!
Ya que no comes, déjame comer. Since you aren't eating, let me eat.
Ya no es rico. He isn't rich anymore.
¡Ya nos veremos! See you soon!
Ya llega el tren. The train is finally / right now / already / soon arriving.
Ya no verás más ese dinero. You'll never see this money again.
¡Ya te arrepentirás! You'll regret this someday!
Ya es necesario tomar una decisión. It's time to make a decision.
Ya, pero es dificil. Yes, but it's difficult.
Ya con goza, ya con dolor. Sometimes with pleasure, sometimes with sorrow.
Ya entiendo. Now I understand.
This is one of the ways that learning a foreign language makes you think differently. The very idea of time in Spanish is just a little different than in English. Ya.
— Sue Burke
Also posted at my professional website, http://www.sue.burke.name