An irritable person gets annoyed quickly or easily. The spark is small; the reaction comes fast.

An irritable person易怒的人 quickly or easily很快又很容易 gets annoyed就生氣。The spark火花 is small很小，the reaction反應 comes fast來得很快。

People often become irritable when they are tired, hungry, too hot, in pain, or under stress, so the word can describe a passing state as well as a habit of temper.

when they are tired, hungry, too hot, in pain, or under stress在累了、餓了、太熱、疼痛或有壓力的時候，People人 often become irritable常常會變得易怒，so所以 the word can describe a passing state這個字可以形容一時的狀態，as well as a habit of temper也可以形容脾氣上的習慣。

It is ordinary English, fine in speech and in writing, and a little softer than calling someone bad-tempered all the time.

It is ordinary English這是很普通的英文，fine in speech and in writing說話和寫作都能用，and而且 than calling someone bad-tempered all the time比起說一個人一直脾氣不好 a little softer要委婉一點。

Though actually, doctors also use irritable for a part of the body that reacts too easily, as in irritable bowel (腸躁症 in Taiwan): the same idea of being set off too fast, but about an organ, not a mood.

Though actually不過，doctors also use irritable醫生也會用irritable for a part of the body that reacts too easily來說身體某個太容易有反應的部位，as in irritable bowel (腸躁症 in Taiwan)像irritable bowel（在台灣叫腸躁症）：the same idea of being set off too fast一樣是太容易被引發的概念，but about an organ, not a mood只是這次講的是器官，不是情緒。

The everyday meaning you will meet first is still about a person's temper.

The everyday meaning you will meet first你最先會遇到的日常意思，is still about a person's temper還是在講一個人的脾氣。