What is the difference between "ещё" and "больше"?

Question

I know they both mean 'more' ? But there useage seems to differ, is there a rule of thumb?

Answer 1

"Ещё" and "больше" intersect only partially and have a lot of usages that are by no means interchangeable.

"Ещё" can mean:

• yet (like in "Я ещё не решил, идти ли мне в институт")
• again (like in "Поцелуй меня ещё".
• so far (like in "она ещё совсем ребёнок")
• something happened quite long ago (like in "замок был построен ещё в 9-м веке")
• there's still some аmount of something left (like "там ещё две котлеты осталось").
• an indication of reproach ("а ещё и вырядилась-то как")

You can not say "поцелуй меня больше", "она больше совсем ребёнок", "я больше не решил", "а больше и вырядилась-то как" etc.

As of "больше" it can mean:

• comparative degree of "big" (like in "У него дом больше").
• comparative degree of "many" (like in "Там больше рыбы").
• with negation like in "Он больше не будет нам досаждать").
• with negative pronoun as in "ты преступник и ничего больше".
• predominantly (like in "Я больше по пятницам выступаю").

Last four sentences can be actually translated with invocation of "more" in English however in Russian text "больше" can not be changed to "ещё".

That's the most frustrating part of learning any language - there's no one-to-one correspondence with lexical units in your native language. One should just memorize.