1、如果不特定指出哪一个，是泛指，“另一个”要用another, 后加可数名词单数。
If you are still thirsty, you may have another cup of tea.(没特定指出哪一杯茶，是泛指。cup是单数。)
another也可+数字+可数复数：The meeting will last another two hours、(再持续两小时)
We need another six desks、(此处两句分别相当于：two more hours; six more desks.)
2、如果只有两个或只有两部分，就给出了范围，其中另一个或另一部分是特指 (other前有the.)， 有如下用法：
第一种，所说内容只有两个：Mrs、Green has two sons, one is interested in math, the other (one/son) is good at science、【只有两个，用the other, 不加s, 后面名词可省略。】又如：This pair of shoes is strange、One is blue, yet the other is green、“这双鞋子很怪，一只蓝色，而另一只绿色。”第二种，只有两部分：此种情况下the other后接可数名词复数，或不接名词而只在the other后加s、Two children went there, but the other children/the others stayed.
Two fifths of the students in our class are boys, the other students/the others are girls.
3、如果没有显示出只有两部分，未给出范围，则是泛指，不加the.
Lei Feng liked helping other people/others、Do you have any other questions?
Alice didn’t like that dress, so she asked to see some others.
other的另一用法：用比较级的形式，体现最高级的含义。
He is taller than any other boy in his class、(划线中boy常用单数) =
He is taller than all ( of ) the other boys in his class、(划线中boy用复数)
他比班里任何男孩都高(他是班里男孩中最高的)。