Which instrument is primarily used for cutting during surgery?

The scalpel is primarily used for cutting during surgery due to its sharp blade, which allows for precise incisions in various tissues. Its design and functionality enable the surgeon to perform controlled cuts needed during procedures. The scalpel's blades come in various shapes and sizes, making it versatile for different surgical applications, from making initial incisions to fine dissection.

In contrast, while the hemostat is important for clamping blood vessels and controlling bleeding, it does not serve the purpose of cutting. Forceps are designed for grasping and holding tissues rather than cutting, and the needle holder is specifically for holding needles during suturing. Therefore, the scalpel stands out as the primary cutting instrument in a surgical setting.