TOIEC Grammar Basics - The 1st conditional
What is the 1st conditional in English?The first conditional form is used to express something that is possible and probable. Like all conditional forms, it contains an "if" clause and a "then" clause.
For example, "If I go to the store, (then) I will buy milk." Meaning, there is a store open, I have the chance to go to the store. It is not definite, but it is probable and possible.
The "if" clause uses the simple present; while the "then" clause uses "will + verb".
"If she passes her exam, she will go to medical school." Meaning, she is taking an exam, but she has studied for it. It is not definite that she will pass, but it is probable and possible.
If the car starts tomorrow morning, then we can go on vacation. Meaning, the car sometimes has problems, but at the moment it is fine, so tomorrow we want to leave, and it is both probable and possible.
Notice that the word "can" replaces the word "will". It is possible to use any present tense modal - although the most commonly used is "will". Also, the word "then" is optional in conditional sentences. We at Scott's English Success recommend that you write it in your formal writing, though.