also用在句中（一般放在be动词和助动词之后,行为动词之前）.
she also is good at English.
she also like English.
too 多用于口语,位于句未或句中,只用于肯定句,其前常有逗号.
They are students,too.=They,too,are students.
否定句为They are students,either.
as well 用于肯定句,通常位于句中或句尾.
He knows French,and he knows English as well. also用在句中（一般放在be动词和助动词之后,行为动词之前）.
she also is good at English.
she also like English.
too 多用于口语,位于句未或句中,只用于肯定句,其前常有逗号.
They are students,too.=They,too,are students.
否定句为They are students,either.
as well 用于肯定句,通常位于句中或句尾.
He knows French,and he knows English as well.