Your bicep is the large muscle on the front of your upper arm, the one that bunches up when you bend your elbow to show your arm. Gyms and everyday English often say bicep for one arm and biceps for both, or just “biceps” either way.

Your bicep is the large muscle on the front of your upper arm你的bicep是上臂前側的那塊大肌肉， the one that bunches up就是會鼓起來的那塊， when you bend your elbow to show your arm當你彎手肘要秀肌肉的時候 Gyms and everyday English often say bicep for one arm健身房和日常英文常常一隻手臂說bicep， and biceps for both兩隻都說biceps， or just "biceps" either way或是不管單雙都直接說biceps

Though actually, the older and more careful word is biceps even for one muscle. That is the Latin form, and it is already singular: bi- “two” + -ceps “head,” because the muscle has two heads where it joins near the shoulder.

Though actually不過其實， the older and more careful word is biceps比較古老、比較講究的說法是biceps， even for one muscle就算只講一條肌肉也一樣 That is the Latin form那是拉丁文的形式， and it is already singular而且本身就是單數： bi- "two" + -ceps "head,"bi-是「二」，-ceps是「頭」， because the muscle has two heads where it joins near the shoulder因為這條肌肉在靠近肩膀的地方分成兩個頭

English speakers later cut off the -s and made bicep, the way they sometimes do when they think a word is plural. Doctors and textbooks still prefer biceps.

English speakers later cut off the -s後來英語使用者把字尾的-s去掉， and made bicep造出bicep這個字， the way they sometimes do when they think a word is plural就像他們有時候誤以為一個字是複數時會做的那樣 Doctors and textbooks still prefer biceps醫生和教科書還是比較愛用biceps

The matching muscle on the back of the arm is the triceps, not a second bicep.

The matching muscle on the back of the arm is the triceps手臂後側對應的那塊肌肉是triceps（三頭肌）， not a second bicep不是第二個bicep