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As is typical for many languages, full conditional sentences in English consist of a condition clause or ''protasis'' specifying a condition or hypothesis, and a consequence clause or ''apodosis'' specifying what follows from that condition. The condition clause is a dependent clause, most commonly headed by the conjunction ''if'', while the consequence is contained in the main clause of the sentence. Either clause may appear first. Different types of conditional sentences (depending largely on whether they refer to a past, present or future time frame) require the use of particular verb forms (tenses and moods) to express the condition and the consequence. In English language teaching the most common patterns are referred to as first conditional, second conditional and third conditional; there is also a zero conditional and mixed conditional. For more general information about the uses of verb tenses, moods and aspects in English, see Uses of English verb forms. ==Overview== In English conditional sentences, the condition clause (protasis) is a dependent clause, most commonly introduced by the conjunction ''if''. Other conjunctions or equivalent expressions may also be used, such as ''unless'' (meaning "if...not"), ''provided (that)'', ''providing (that)'' and ''as long as''. Certain condition clauses can also be formulated using inversion without any conjunction; see below. The apodosis, expressing the consequence of the stated condition, is generally the main clause of the sentence. Depending on the sentence type, it may be a statement, question, or order. It may appear before or after the condition clause: ::If I see him, I will tell him. (declarative sentence, condition first) ::I will tell him if I see him. (declarative sentence, condition second) ::If you saw him, would you tell him? (interrogative sentence, condition first) ::Would you tell him if you saw him? (interrogative sentence, condition second) ::If you see it, photograph it. (imperative sentence, condition first) ::Photograph it if you see it. (imperative sentence, condition second) As with other dependent clauses in English, it is common for a comma to be used to separate the clauses if the dependent clause comes first (as is done in the above examples). See . It is possible for the consequence clause to appear alone in a sentence, without a condition clause, if the condition has been previously stated or is understood from the context. It may also be shortened by verb phrase ellipsis; a minimal conditional sentence could therefore be something like "Would you?" or "I would." 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「English conditional sentences」の詳細全文を読む スポンサード リンク
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