if; would(used only with the inf. or past tense of a verb; used in speaking of something that will, may or might happen (e.g. if a certain condition is met); used to express a preference, opinion etc. politely • If I asked her to the party, would she come?; I would have come to the party if you'd asked me; I'd be happy to help you; I would do it this way; It'd be a shame to lose the opportunity; I'd prefer to go tomorrow rather than today); should
would(частица • at that time, any geometrical system not in absolute agreement with that of Euclid's would have been considered as obvious nonsense • in order to produce such an amount of energy, this thermal power plant would require as much as 100 tons of coal); could(частица • without the friction between our shoes and the floor we could not walk)