Pitman's Commercial Spanish Grammar (2nd ed.)

Si (if and whether).

Si used for "whether" may be followed by a verb in any mood and tense as in English --

No sé si habrá buena cosecha este año: I do not know whether there will be a good crop this year.

No pudo, or supo, decirme si me entregaría los pagarés para la fecha convenida: He could not tell me whether he would be able to hand me the promissory notes for the date agreed upon.

Si used as the conditional "if," is followed by the verb in the present indicative or imperfect subjunctive, as --

Si viene hoy le pagaré: If he comes today, I shall pay him.

Si viene mañana le pagaré[208]: If he comes tomorrow I shall pay him.

Le dije que si viniese le pagaría: I told him that if he came I should pay him.

Footnote 208: When the action refers to the future the "future subjunctive" may be used instead, but this is rarely done. It emphasises the uncertainty.

The sense will determine the tense to be used.

Notice the following idiomatic uses of si (not conditional) --

Si soy (fuí) malo! Well, I am (was) wicked!
¡Si será (sería) tan necia! Can (could) she be so foolish!
¿Si vendría? I wonder will he come!
¡Si se lo había dicho yo mil veces! But I had told him so many times!

Other idiomatic uses of this si will be learnt by practice (all more or less pleonastic as in the above examples).

We have said that "but" is translated by sino after a negative unless a finite verb follows. Therefore, "Not to buy but to sell" is translated "No comprar sino vender."

After a negative a finite verb may be preceded by sino que instead of pero in cases like the following examples --

No compró sino que vendió: He did not buy but (on the contrary) he sold.
No sólo que es barato sino que es de muy buena calidad:
Not only is it cheap, but it is (also) of a very good quality.

Ni ... ni -- "neither ... nor" (same as all negative words) when following a verb requires No to precede the verb, as --

No acepta ni esto ni aquello: He accepts neither this nor that.

But -- Ni esto ni aquello quiere aceptar.

Pues -- "seeing that" or "since" is used often for "then," "but," "well" (used as an interjection).

Pues que lo haga: Let him do it then.

Quiso desobedecerme, pues vera su falta: He would disobey me, but he will see his fault.

Pues (or pues bien) ¡que hay ahora! Well! what is the matter now?

We shall conclude the lesson with the different meanings of Ya (sometimes used also redundantly). They are given for the sake of completeness although Ya in its different uses belongs to different parts of speech --

Ya lo ha hecho: He has done it already.
Ya lo hará: He will do it yet.
Ya no se hace esto: This is done no longer.
Ya consienten, ya rehusan: Now they consent, now they refuse.
Ya consientan, ya rehusen: Whether they consent, etc.
Haré cuanto quieras si ya no me pides lo imposible:
I shall do anything you wish if you do not ask (unless you ask) me for impossibilities.
Ya que escribió: Since (seeing that) he wrote.
Ya ve V.: You see now.
Ya voy: I am coming.
Ya se ve: It is evident.
Ya, ya: Yes, of course.