Conditional sentences are statements that express a hypothetical situation and the result that would occur if that situation were to happen. There are three main types of conditional sentences: zero conditional, first conditional, and second conditional.
Zero Conditional: The zero conditional is used to talk about things that are always true, and it is formed with two present tense clauses connected by "if" or "when." For example: "If you heat water to 100 degrees Celsius, it boils." This sentence expresses a general truth that is always true when the condition is met.
First Conditional: The first conditional is used to talk about things that are likely to happen in the future, and it is formed with a present tense clause (the condition) and a future tense clause (the result), connected by "if" or "when." For example: "If it rains, we will stay inside." This sentence expresses a possible outcome that is likely to happen if the condition is met.
Second Conditional: The second conditional is used to talk about things that are unlikely or impossible to happen in the present or future, and it is formed with a past tense clause (the condition) and a conditional tense clause (the result), connected by "if." For example: "If I had a million dollars, I would buy a house." This sentence expresses a hypothetical situation that is unlikely to happen, but if it did, it would result in a particular outcome.