(1) 二擇一：one ... the other
You have two choices: one is to stay in the current job and work harder; the other is to quit and find another job!
(2) 之外的「另一個」: one... another, some... another.
We have solved several problems, but there is another issue we need to face.
(3) 其他一些：some... others 或 other + 複數名詞
The students in the front rows raised their hands, but the other students remained silent.
Some students raised their hands, but (the) others didn’t.
→ 加 the 是強調「可知的」；不加 the 則是單純與 some 的語意對應。