stammer: implies a temporary inhibition from fear, embarrassment, or shock: ~ed his thanks, overcome with embarrassment.


stutter: is likely to suggest a habitual defect characterized by repetition of sounds, but it may apply to a similar manifestation due to a temporary cause: ~s when excited; or even, as may stammer, to something suggesting the pattern of a stutterer: the engine ~ed then came to life.       (如把我说成"我我")  (pattern模式，指固定样子)


stammer: 表示暂时的不流畅(inhibition)，由于害怕尴尬震惊等，stutter: 表示习惯性的缺陷，即发音重复，但也可表示暂时性的(缺陷)；还可表示像结巴的样子


记忆方法: 1) Shi Sheng失声<==结巴

              2) 结巴的意思是讲话不顺畅mean to speak stumblingly.Shi Sheng失声<==结巴     (stumble: 说话结巴出错: he stumbled over every sentence他每句都结结巴巴)