本文針對日語裡表示推量的句尾助詞「かな、かしら」，在與表示推量的情態詞「だろう、かしら、かもしれない」的對照之下，討論其語意內涵（用語意屬性〈不/確定〉、〈推量〉、〈男/女性語〉來加以分析）與言談功能（包括從「不定推量」到「微弱詢問」的語意擴張）。本文的討論包括：（一）日語的句尾助詞在語意內涵及言談功能上與談語者的情態及客氣有關，因而也與日語的情態詞發生密切的關係；（二）句尾助詞「かな、かしら」與情態詞「かどうか、だろう、かもしれない、らしい」可以用〈±確定〉、〈±推量〉、〈±男性用語〉這幾個語意屬性與正負兩位來分析並加以區隔；（三）這樣的屬性分析不但可以說明這些詞語能否與疑問助語「か」、情態副詞「恐らく、ひょつとすると、もさか」、以及疑問詞（如「誰」）的疑問用法或不定用法連用，而且還可以詮釋如何能在「不定推量」經過語意或語用擴張獲得「微弱詢問」與「客氣詢問」的言談功能。

The present paper discusses the semantic content of the Japanese final particles “kana” and “kasira”, in terms of the three semantic features-<±suppositional>, <±certain>, <±male>, and further, investigates their discourse function, including the semantic extension from “uncertain supposition” to “weak question”, in contrast with other synonymous modality expressions such as “kadooka, daroo, rasii, kamosirenai”. As a result, the following conclusions have been reached: (1) Japanese modality expressions, including final particles, which have been dealt only within semantics and syntax, prove to have implications in pragmatics as well, especially with regard to politeness strategy; (2) not only the semantic content of the final particles “kana, kasira” but also that of the modality expressions “kadooka, daroo, rasii, kamosirenai” can be distinguished and identified by resorting to the three semantic features with two values, namely, <±suppositional>, <±certain> and <±male>; (3) the proposed analysis of the Japanese final particles and modality expressions not only accounts for the cooccurrence restrictions between these expressions and the interrogative particle “ka”, the modal adverbs “osoraku, hyottosuruto, masaka”, and the interrogative and indefinite use of the indeterminative pronominal “dare, nani”, but also sheds light on the process of how these expressions acquire their pragmatic as well as semantic extensions (i.e. changing suppositional statements into weak questions and polite questions).