Either is a determiner, pronoun, adverb or conjunction used to indicate one or the other of two people or things.
Common usages:
1. Either...or... - used to indicate a choice between two possibilities
2. Either (of) - one or the other of two people or things
3. Either way - in any case
4. Me either - informal agreement with a negative statement
哎呦喂，either这个词儿可太常见了，但好多人都整不明白。说白了就是"两者中任何一个"的意思，可以当限定词、代词、副词或者连词使。
常见用法咱给您掰扯掰扯：
1. either...or... - 表示"要么...要么..."，二选一的意思。举个栗子："You can either stay or leave"翻译成"您爱待着就待着，想走就走"
2. either (of) - "两者中随便哪个都行"。比如："Either of the options is fine"就是"这俩选项选哪个都成"
3. either way - "反正都行"或者"横竖都一样"。比如说："Either way, we'll be there by 8"翻译成"甭管咋地，8点前咱准到"
4. me either - 这个可太常用了，表示"我也不"。比如人家说"I don't like it"，你回"Me either"就是"我也不稀罕"
注意哈，这词儿跟"neither"是哥俩好，一个肯定一个否定。要是整不明白，直接记"either是二选一，neither是俩都不要"就完事儿了！