Лекции по теоретической грамматике английского языка. Тивьяева И.В. - 73 стр.

UptoLike

Составители: 

73
dimly, she saw the picture of a man walking up a road (Christie) the modal word
perhaps is not a sentence member, but if we remove it, the meaning of the
utterance will change – it will be just a statement of the fact.
Academician Shcherba states that there are some words that do not belong to
any part of speech. Prof. Ilyish regards the words yes, no and please as standing
outside the part of speech system. This point of view is also supported by Prof.
Smirnitsky.