Speechlessness is the noun for the state of being speechless — the wordlessness itself, treated as a thing you can talk about. Because it names a state rather than describing a person, it feels distant and analytical: 'his speechlessness surprised her', 'a moment of speechlessness followed'. Writers use it when the silence is the subject of the sentence, not the person. It is rare and heavy — five syllables, three word-parts stacked up. English speakers usually dodge it and say 'silence' instead, or restructure with the adjective: not 'her speechlessness lasted a minute' but 'she couldn't speak for a minute'. Be aware of that preference; it is the natural-sounding choice. Where you do meet the word is in serious writing about emotion, in literary criticism, in psychology, and in writing about trauma or awe, where 'silence' would be too plain and the writer wants to point at the failure of words specifically. That is its real home: it does not just mean quiet, it means language broke down.

無言、說不出話的狀態（名詞）。中文常用「一時語塞」「啞口無言」來翻，但注意這是把「說不出話」當成一個東西來講，偏學術、文學用語，口語不會這樣說。