"So do I" is another way of saying "me too" "I think so" is another way of saying "I'm not sure that's what I think" "ain't" this is English slang, instead of saying "no I will not do this" you would say "ain't gonna do this" don't use it if you're trying to sound professional. For example, a Job interview.

"So do I" and "I think so" are standard English expressions. "Ain't" is not. So, you would sound very strange if you tried to use slangy "ain't". Make sure you know standard English well before you start using slang. "So do I" means "I do the same thing too." It's a response. "I think so" means "What has just been said is my opinion". It also comes after a preceding comment.

"I want to improve my level of English, so any help would be welcome." "So do I" means "I do too / also" You can say this to indicate agreement in any case, and with any verb (not just do) e.g. "He wants to go to Brazil. So do I" "I think so" = "I also think the same" e.g. "Do you think Brazil is the best country in the world? I think so." "I think so" is the answer to a question when you agree - not with certainty but probably. "ain't" is street slang for "isn't" or "hasn't". e.g. "He ain't got a chance of survival" "He ain't stupid". You will find that most teachers don't speak this way, even to their friends. To use "ain't" is a marker that you are "working class" in the UK. I think "ain't" is also used in America as street slang but you would have to ask an American exactly which groups use it. I don't recommend you use it.

"So do I" is the same as "me too" (eu também) "I think so" is the same as.. "I think" (eu acho) "Ain't" is the contracted form of "are not", "am not" (não sou, não são), but it is informal. Ex: -I love sushi -So do I / me too -This band is awesome, right? -I think so. -Where are they? -They aren't here. / They are not here.

level* help* "so do I" = i also (yo también......) " I think so" = pienso que...... (to think = to wonder, ponder, deliberate mentally) "ain't"= isn't it (no es así..) this is very much American. ''Isn't' it is British (and better to say)