If = jeśli (jeżeli) at all. If we say "if human = animal" - "Jeśli człowiek to zwierzę", must be some addition to this sentence, for example: "Jeśli człowek to zwierzę, jestem kotem." - "If a human is an animal, I am a cat." That's why "czy" isn't "if". In that sentence without question will be: "Człowiek to zwierzę." - "A human is an animal". To make a question we need to add the word "czy" to the Polish sentence: "Czy człowiek to zwierzę?", and to change the word's positions in the English sentence: "Is a human an animal?". That's why, "czy" isn't "is". In this example we see, that the constructions of making questions is different in Polish and English. I can't translate "czy" in English literally. I'm sorry for my mistakes in English. P.S. If somebody knows Russian, "czy" is "ли" in Russian.