Conditional sentences usually consist of two clauses: the condition clause, which expresses the condition, and the result clause, which expresses the hypothetical consequence that would follow if the condition were met. For example:

There are different types of conditionals and each serves a specific function:

We use zero conditionals to express general truths such as scientific facts, typical behaviors, explanations, guidelines, advice, orders, instructions, etc. Pay attention to the following examples:

The zero conditional structure consists of an 'if-clause' with a simple present verb, and a main clause with a simple present verb.
Modal verbs such as can, might, could, may can also be used in the main clause of a zero conditional sentence..

The first conditional mood is used to express a possible condition and its probable result. This structure is often used to talk about future events that may or may not happen depending on whether a certain condition is met. Take a look at the examples:

The 'if-clause' in the first conditional mood can be in simple present, present continuous, present perfect, and present perfect continuous tense. The verb in the main clause can be in future tense or a modal such as will, can, may, must, etc.
Additionally, in some cases, imperatives can be used in the main clause of a first conditional sentence to express a command or instruction.

The second conditional is used to express hypothetical situations that are unreal or are unlikely to happen. This structure is often used to talk about present or future dreams or situations that are imagined but not happening.

In the second conditional mood, the verb in the condition clause can be in the simple past, past continuous, or past modal form. The main clause can be constructed using past modal verbs together with the base form of the verb.
Take a look at the examples:

The third conditional mood is used to express hypothetical situations in the past which are unreal and impossible to happen because they are about events in the past that cannot be changed. For example:

In the third conditional mood, the condition clause can contain a past perfect, or a past perfect continuous verb. In some cases, 'could have + past participle' can also be used in the condition clause. The main clause typically uses 'would have', 'might have, or 'could have' followed by a past participle. Here are some examples:

Mixed conditionals are a type of grammatical structure used to express hypothetical situations that are unreal or unlikely to happen. In a mixed conditional sentence, the condition clause and the main clause are not in the same tense.

Mixed conditionals can be constructed in two ways. The first way is to use a past condition with a present result, while the second way is to use a present condition with a past result. The structures are as follows:

There are two ways to construct a conditional sentence: by starting with the condition clause or starting with the main clause.
If the conditional sentence starts with the main clause, no comma is needed between the two clauses.
If the conditional sentence starts with the condition clause, a comma is needed between the two clauses.
Take a look at the examples below: