This is the 614th most frequent Chinese word.
司機
Driver.
司機 is used here to refer to a person who drives a vehicle as their occupation or role, emphasizing their professionalism.
這位司機非常專業，開車平穩又安全。
This driver is very professional, driving smoothly and safely.
司機 is used here to denote the driver making a logical or strategic decision to alter their driving path.
因為塞車，司機決定改變行車路線。
Due to traffic jam, the driver decided to change the route.
司機 in this sentence specifies a professional specializing in operating a particular type of vehicle, namely a race car driver.