Tetchiness is the noun: the state or quality of being easily annoyed. You use it when you want to name the mood itself rather than describe a person. It shows up in two ways. First, about one person on one occasion: 'There was a tetchiness in his voice', 'I apologised for my tetchiness that morning.' Second, and very commonly in the news, about the mood of a group or a relationship: 'the tetchiness of the negotiations', 'growing tetchiness between the two parties'. It is uncountable, so it takes no plural — tetchinesses does not exist. Like the adjective it comes from, it names something small and often temporary. Writers reach for it because it is gentler and more precise than anger: it tells the reader that people were short with each other, not that anyone lost control. It is a formal, written word; in conversation people say 'he was in a mood' or 'things got a bit sharp'.

不耐煩、易怒的狀態（名詞）。可以指某人當下的火氣（語氣裡有一股不耐），也常用來講談判或關係的氣氛「火藥味」。不可數，沒有複數。