"But for" means "if it were not for/if it hadn't been for":
"He looks as if he French" means "Fact - it is perfectly possible that he is":
"He looks as if he were French" means "Non-fact - we know he isn't":
"Otherwise" means "if this doesn't happen/didn't happen/hadn't happened":
A combination of types 2 and 3 is possible:
A suggestion in type 2 is a little more polite than a suggestion in type 1, just as would you is a more polite request form than will you:
Conditional sentences have three parts:
If + should can be used in type 1 to indicate that the action, though possible, is not very likely:
If + subject + auxiliary can be replaced in formal English by inversion of auxiliary and subject with if omitted:
The Present Conditional Tense is formed with would/should + infinitive for the first person and would + infinitive for the other persons:
The Present Conditional Tense is formed with would/should and the Perfect Infinitive:
The Present Conditional Tense is used in conditional sentences:
We cannot use unless in place of if...not when if...not doesn't mean 'except if':
We often use unless (never if...not) to introduce and afterthought:
When if is used to mean as/since, a variety of tenses can be used in the main clause:
Условное предложение второго типа имеет вид: The verb in the if-clause is in the Past Tense; the verb in the main clause is in the Conditional Tense:
Условное предложение третьего типа имеет вид: The verb in the if-clause is in the Past Perfect Tense; the verb in the main clause is in the Perfect Conditional: