But after such verbs as dudar "doubt" and negar "deny", with essentially negative meaning, the subjunctive is used when the main verb is in the positive, and the indicative when it is in the negative: dudo que sea posible "I doubt that it's possible".
2. Clauses serving as adverbs: after a number of conjunctions, such as:
a condición que "on condition that"
a fin (de) que "in order that"
a menos que "unless"
aun cuando "even if"
para que "so that"
supuesto que "supposing that"
3.52 Significant use of the subjunctive is found in the following types of clauses:
1. Clauses used as adjectives, giving the clauses the meaning of:
a) A desired characteristic or purpose: busco un libro que sea interesante "I'm looking for a book that'll be interesting". b) Uncertainty or doubt: las expresiones que Uds. hayan olvidado "the expressions you may have forgotten". This type of clause is especially frequent after indefinite and concessive expressions: cualquier libro que escriba "whatever book he may write"; por rico que sea "no matter how rich he may be". It is also found after superlatives or equivalent expressions: el libro más interesante que haya "the most interesting book there is".
2. Clauses used as adverbs, giving the meaning of:
a) Intent, purpose, or anticipation: hable Ud. de manera que todos le oigan "talk in such a way that all can hear you"; aunque venga, no nos lo enseñará "even though he may. come, he won't show it to us".
b) Futurity: cuando venga, dígaselo "when he comes, tell it to him".
3.53 Conditional sentences. If a sentence contains a clause beginning with si "if", the tense of the verb in this clause is determined by the tense of the verb in the main clause, normally as follows:
| If the main clause has a verb in the: |
The "if"-clause has a verb in the: | |
| Present | Present | |
| Imperative | ||
| Future | ||
| Imperfect | Imperfect | |
| Preterite | Preterite | |
| Conditional | Past Subjunctive (-ra or -se) |
Thus: si está aquí, trabaja "if he's here, he's working"; si estaba aquí, trabajaba "if he was here, he was working"; si está aquí mañana, trabajará "if he's here tomorrow, he'll be working"; si estuviera aquí, trabajaría "if he were here, he'd be working". A main verb indicating a condition contrary to fact may also be in the -ra form of the subjunctive: si estuviera aquí, trabajara "if he were here, he'd be working".
3.6 Minor clauses, which do not conform to the customary structure of clauses, are chiefly of the following two types:
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