Sentence examples for three additional from inspiring English sources

"three additional" is a correct and usable phrase in written English.
It can be used to modify a noun to indicate there are three more of that noun. It can also be used to describe an action or item that is in addition to a previous set. Example: "We need three additional chairs for the meeting." In this sentence, "three additional" modifies the noun "chairs" and indicates that there are already some chairs, but we need three more. Another example: "The project already has two stages completed, and we're planning on adding three additional stages to make it more comprehensive." In this sentence, "three additional" describes the action of adding more stages to the project, indicating that there were already two completed.