Usefulness is the noun from useful: the quality of being useful, or how much use something has. You talk about the usefulness of a tool, a rule, a website, an idea.

Usefulness is the noun from usefulusefulness是useful的名詞形式: the quality of being useful, or how much use something has指有用的這種特質，或是某個東西有多少用處。You talk about the usefulness of a tool, a rule, a website, an idea你會說一個工具、一條規則、一個網站、一個點子的usefulness。

It often shows up when someone is judging or arguing about worth — "They questioned the usefulness of the new form" means they doubted it did any good. A very common phrase is "to outlive its usefulness", said about something old that used to help but no longer does: "That old printer has outlived its usefulness." Usefulness is not a thing you can count, so it has no plural and takes no "a" — say "its usefulness", "the usefulness of", never "a usefulness" or "usefulnesses".

It often shows up when someone is judging or arguing about worth這個字常出現在有人在評斷或爭論價值的時候 — "They questioned the usefulness of the new form"「They questioned the usefulness of the new form」 means they doubted it did any good意思是他們懷疑這個新表格到底有沒有用。A very common phrase is "to outlive its usefulness"有一個很常見的說法是「to outlive its usefulness」, said about something old that used to help but no longer does用來形容某個東西以前有用、現在已經沒用了: "That old printer has outlived its usefulness."「That old printer has outlived its usefulness.」 Usefulness is not a thing you can count, so it has no plural and takes no "a"usefulness不是可數的東西，所以沒有複數，也不能加「a」 — say "its usefulness", "the usefulness of", never "a usefulness" or "usefulnesses"要說「its usefulness」「the usefulness of」，不能說「a usefulness」或「usefulnesses」。

It is a somewhat formal, thinking-out-loud sort of word; in ordinary talk people just say "how useful it is".

It is a somewhat formal, thinking-out-loud sort of word這是一個有點正式、像是在自言自語思考時會用的字; in ordinary talk people just say "how useful it is"平常說話大家就直接說「how useful it is」。

Note that usefulness is about being helpful for a job, not about being valuable in money — an old photo can be precious with almost no usefulness at all.

Note that usefulness is about being helpful for a job, not about being valuable in money要注意usefulness講的是對某件事有沒有幫助，不是金錢上值不值錢 — an old photo can be precious with almost no usefulness at all一張老照片可以很珍貴，卻幾乎沒有usefulness。