The word "Nightstool" is spelled as /naɪt.stuːl/. This word is a combination of two words, "night" and "stool". The word "night" refers to the time of day when it is dark outside, typically from sunset to sunrise. And the word "stool" refers to a seat without a backrest or arms. Therefore, "nightstool" is a term coined to describe a type of stool used during the night. It is important to remember the correct spelling of words to ensure clear communication and avoid confusion.