What is the difference between all the words for tools / devices?

Question

There is too many words for 'tool' that I am having hard time figuring out when to use which, or if some of them are just synonyms, meaning essentially the same thing. So far I know at least the following words (with dictionary definitions, and example sentences with rough translations from Tanaka Corpus):

1. 器具{きぐ} = utensil; apparatus; implement; device; gadget
   • e.g. 「その学校は最新の体育器具を備えている。」 = "That school is equipped with the latest gymnastics apparatus."
2. 道具{どうぐ} = tool; implement; instrument; utensil; apparatus; device
   • e.g. 「それを開ける道具が必要です。」 = "We need a tool to open it with."
3. 器械{きかい} = instrument; appliance; apparatus
   • e.g. 「血圧計は大切な検査器械です。」 = "The sphygmomanometer is an important diagnostic instrument."
4. 装置{そうち} = equipment; installation; apparatus; device
   • e.g. 「これは電気を作る装置だ。」 = "This device produces electricity."
5. 用具{ようぐ} = tools; implements
   • e.g. 「ペンや鉛筆は筆記用具である。」 = "Pens and Pencils are the tools of writing."

Judging by the amount of example sentences I found for each of these words, 用具 and 装置 are not very common words(?).

There is this Japanese dictionary that discusses the differences between some of the words (http://dictionary.goo.ne.jp/leaf/thsrs/6332/m0u/), and if I understood correctly the meanings are:

• 道具 means widely used tools, and generally means tools with simple structure that can be used with hands (手で扱う簡単な構造のもの). An instrument.
• 機械 or 器械 are used when referring to tools / devices with more complicated structure.
• 用具 and 道具 can often be used interchangeably, but 用具 is mostly being used to refer to sports and studying (学習) tools. An instrument.
• 器具 refers to type of 器械 with simple structure and small scale. E.g. gas, electric and medical equipment, and うつわもののこと?. An appliance.

Firstly, if 器具 is defined as above, why is it used in the example sentence 「その学校は最新の体育器具を備えている」? Wouldn't 用具 be more appropriate in this context? Are 機械 and 器械 synonyms, i.e. can they be used interchangeably? Also, how does 装置 fit in all of this?

I hope someone can explain this, as I find it confusing.

EDIT: And now I found another word that seems to have quite similar definition compared to the others:

6. 設備{せつび} = equipment; device; facilities; installation.
   • e.g. 「この学校は暖房設備がない。」 = "This school has no heating."

Answer 1

All what you've mentioned above are common words. Despite being synonyms, each of those words has different shades of meaning even when refers to the same object. I could roughly group them into several clusters as follows:

道具 / 器具

They lay stress on direct human manipulation, typically fulfill their purposes by (wholly or partially) being handled freely and physically. You're correct that 道具 is the most widely used word for almost any kind of tools, though I hesitate to use the word for something not handy at all, like supercomputers or jet engines.

Since 器 carries a connotation of "vessel", 器具 gets along better with implements that serve their purpose while staying put. (Of course, they might well be portable when not in use.)

A notable feature of 道具 is that it's the only one among all these words that has figurative meaning.

他人を道具として使う utilize others as tools

用具

It doesn't have complicated nuance (just "tool"), but has somewhat odd grammatical status. If you translate it literally, it should be "tool-for", and could be paraphrased in Japanese as ～用の道具. If you see a 用具入れ, it must be a box or cabinet stores "tools for X" (X = writing, drawing, cleaning, or other specific purposes) but not a multi-purpose toolbox as a 道具入れ is.

機械 / 器械

These words are for mechanical instruments, but the two are usually not interchangeable. 機械 must have "clockwork" components that work in irrelevant way to the physical force people have input. If it lacks them, however precisive it be, it will be called as 器械. Thus, many machines today you press buttons to start up are 機械, and 器械 is relatively less used in regular life.

The sphygmomanometer in your example is a genuine 器械, but if it started to speak and automatically give a health checkup, I'd rather call it 機械.

Note that, however, 器械 can stand for gymnastics apparatus. It's a fixed terminology.

装置 / 設備

They mainly tell that it is a stationary equipment works by its own. The devices people usually don't casually decompose or detach, say, air-conditioners or GPS systems, are typical examples of 装置. 設備 means some big installations built in to the building.

The entire building serves as a facility is not 設備 but 施設{しせつ}. And "device" in wearable devices often doesn't fit the sense of 装置. We usually call those techie "devices" simply as デバイス.

Answer 2

To simplify the issue, I think it’s better to understand the meanings of tool / machine -related Japanese words from their usage rather than detailing their definitions:

道具 is the most popular Japanese word for general tools and instruments, i.e. 大工道具 - carpenter’s tools, 左官道具 - plastering tools.

用具 / 用品 is equivalent to 道具 with a bit more modern and specific tonality, i.e. 運動用具 – sporting goods, 筆記用具 - writing tools, 台所用具 - kitchen utensils.

器具 is equivalent to 用具 with a more mechanical tone, e.g. 運動器具 - sporting equipment, 電気/ガス器具 – electric / gas appliance, 照明器具 – lighting equipment, 医療器具 – medical equipment.

機械 means machine, e.g. 工作機械 - machine tool, 掘削機械 – drilling machine.

装置 means device, apparatus, e.g. 安全装置 – safety device, 発火装置 - ignition device, 電動装置 - electric power device /apparatus.

設備 is a compound of 機械, 器具, and 装置 that make up a facility to serve for a specific purpose.