εἰ [90 verses](conj) "If" is ei, which is the particle used to express conditions "if" (with the indicative, implying nothing about its fulfillment) or indirect and direct questions, "whether." With the subjunctive and a result (apodosis) indicates a repeated action or a vivid future action.  It also means "if ever," "in case," and "whenever." In citing a fact, it can mean "as sure as" or "since."  It is combined with various conjunctions to create derivative conditions. When appearing as εἰ δὲ (literally, "if however") the sense is "if this...then that." The construction εἰ δὲ μή . . means "otherwise." The construction  εἰ οὖν has the sense of "if so." However, it is also used to express a wish. After verbs of wonder, delight, indignation, disappointment, contentment, and similar emotions, it is use instead of ὅτι, to express the object of the feeling in a hypothetical form, "that" with the indicative (not subjunctive). After ὅτι, it introduces a quotation where we use quotation marks. With the future tense, it is used for emphasis, a warning, or an intention.  When this word is paired with the conjunction translated as "but" or "however," the structure works like an "if then" statement in English.  With verbs of desire and emotion and the indicative in the second clause, the sense is "that." With an imperative, it is used to express a wish. The sense is "I wish that." With the future tense indicative, it is used for emphasis, a warning, or an intention. The emphasis clause is after the main statement. -- The "if" with  indicative verbs to express conditions "if" (implying nothing about its fulfillment) or indirect and direct questions, "whether. With verbs of possibility to implied repeated condition or a vivid future one. "It also means "if ever" and "whenever." When citing a fact  the sense is more  "whether," "since" or "as sure as."