A motorcyclist is a person riding a motorcycle. The word points at the person, not the machine. It has a slightly formal, outside-looking-in feel — it is the word the news uses, and the police, and the hospital: 'a motorcyclist was injured on Highway 9', 'motorcyclists must wear helmets'.

A motorcyclist is a person riding a motorcyclemotorcyclist是指騎機車的人 The word points at the person, not the machine這個字指的是人，不是車子 It has a slightly formal, outside-looking-in feel這個字帶點正式、旁觀者的味道 — it is the word the news uses, and the police, and the hospital:——是新聞、警察、醫院會用的字 'a motorcyclist was injured on Highway 9', 'motorcyclists must wear helmets'.像『a motorcyclist was injured on Highway 9（一名機車騎士在9號公路受傷）』、『motorcyclists must wear helmets（機車騎士必須戴安全帽）』

Riders themselves usually don't call each other motorcyclists. Among friends they say 'rider', or 'biker'.

Riders themselves usually don't call each other motorcyclists騎車的人自己通常不會這樣互相稱呼 Among friends they say 'rider', or 'biker'.朋友之間會說『rider』，或『biker』

But be careful with 'biker': in American English especially, biker often suggests a certain kind of person — leather jacket, big loud bike, maybe a club — so it carries a picture with it that 'motorcyclist' does not. 'Motorcyclist' is neutral and safe; anyone on a motorcycle is one, in a suit or in leathers.

But be careful with 'biker'不過要小心『biker』這個字 in American English especially, biker often suggests a certain kind of person特別是在美式英語裡，biker常常會讓人聯想到某一種人 — leather jacket, big loud bike, maybe a club ———皮夾克、大聲的重型機車，搞不好還有幫派—— so it carries a picture with it that 'motorcyclist' does not所以它帶著一種『motorcyclist』沒有的畫面 'Motorcyclist' is neutral and safe『motorcyclist』是中性、安全的說法 anyone on a motorcycle is one, in a suit or in leathers不管穿西裝還是穿皮衣，只要騎機車就是一個motorcyclist

One more thing: the word covers the person driving. If someone is sitting behind, that person is a passenger, or in British English a pillion — not a second motorcyclist.

One more thing還有一點 the word covers the person driving這個字指的是騎車、操控車子的那個人 If someone is sitting behind如果有人是坐在後座 that person is a passenger, or in British English a pillion那個人是passenger（乘客），英式英語裡叫pillion — not a second motorcyclist.——不是第二個motorcyclist