English has three kinds of connecting words, and one question sorts them: what comes next? A conjunction takes a full clause. A preposition takes a noun. A connective adverb needs a full stop or a semicolon in front of it. Although, despite, and however all mean roughly the same thing, yet you can't swap them — the plugs are shaped differently.
Choosing by meaning gets confusing. Choosing by shape doesn't. Although needs a full clause behind it, subject and verb included. Despite needs a noun, or an -ing form. However needs the previous sentence closed off with a full stop or a semicolon first; after that it usually opens its own sentence, though it can also sit mid-sentence or at the end. One idea, three ways to plug it in, and once you see the shapes you stop memorizing pairs.
同じ内容を3通りでOne idea, three plugs
Although it wasこの文の組み立て【過去進行】過去のある時点で進行中だったことを言う形。背景を述べておいて、そこへ別の出来事が割り込む形でよく使う。raining, we went out.
雨が降っていたが、私たちは出かけた。
接続詞。後ろは it was raining という文。A conjunction, so a full clause follows: "it was raining."
Despite theなぜ the なのか【その場で一つに決まる】話し手と聞き手のいる状況で、どれを指すか一つに決まるから the。日本語なら「（例の）」「うちの」を補って読むと感覚が近い。 rain, we went out.
雨にもかかわらず、私たちは出かけた。
前置詞。後ろは the rain という名詞。A preposition, so a noun follows: "the rain."
It wasこの文の組み立て【過去進行】過去のある時点で進行中だったことを言う形。背景を述べておいて、そこへ別の出来事が割り込む形でよく使う。raining. However, we went out.
雨が降っていた。しかし私たちは出かけた。
接続副詞。前をピリオドで切って、独立した文の頭に置く。A connective adverb, so the previous sentence ends first.
接続詞(後ろは文)
and / but / because / although / when / if。後ろに主語と動詞がそろう。And, but, because, although, when, if. A subject and a verb follow.
We stayed home because the trains had stopped.
電車が止まっていたので家にいた。
前置詞(後ろは名詞)
despite / in spite of / because of / during。後ろは名詞か動名詞。Despite, in spite of, because of, during. A noun or an -ing form follows.
We stayed home because of the train delays.
電車の遅れのせいで家にいた。
接続副詞(前を切る)
however / therefore / moreover / as a result。前の文をピリオドかセミコロンで終える。However, therefore, moreover, as a result. The sentence before it has to end.
The trains had stopped. Therefore, we stayed home.
電車が止まっていた。だから家にいた。
よくある間違い / Common Mistake
×Despite it was raining, we went out.
雨が降っていたが、出かけた。(のつもりで)
○Although it was raining, we went out.
雨が降っていたが、出かけた。
despite の後ろに文を置いた形です。despite は名詞用のプラグなので、it was raining は差さりません。直し方は2つ。文を残すなら although に替える。despite を残すなら the rain という名詞に替える。despite the fact that it was raining という逃げ道もありますが、長くて硬いので、書き言葉でも好まれません。
This puts a clause where despite wants a noun. The plug doesn't fit. You have two repairs: keep the clause and switch to although, or keep despite and shrink the clause to "the rain." There is a third route, "despite the fact that it was raining," but it's long and heavy, and even careful writers tend to avoid it.
because of + noun〜のせいで／〜のおかげで理由を名詞で言う前置詞の型。because は後ろに文が来るので別物。The preposition route to a reason. Because takes a clause instead.
in spite of + noun〜にもかかわらずdespite と同じ名詞用プラグ。3語ぶん長いので、書き言葉では despite が好まれる。Same noun socket as despite, just three words long. Writing tends to prefer despite.
as a resultその結果接続副詞の型。前をピリオドで切ってから置く。A connective adverb, so the sentence before it has to close first.
on the other handその一方で対比の接続副詞。文を独立させて使う。The contrast adverb. It heads its own sentence.
That said, ...とはいえ、however のくだけた代役。会話とカジュアルな文章で頻出。A relaxed stand-in for however. Common in speech and casual writing.
まとめ / Summary
後ろが文なら接続詞、名詞なら前置詞、前を切るなら接続副詞。Clause behind it: conjunction. Noun behind it: preposition. Full stop in front: connective adverb.
although / despite / however は意味が近くても入れ替えられない。Although, despite, and however are close in meaning and not interchangeable.
従属接続詞は節ごと文頭に出せる。等位接続詞は出せない。Subordinating conjunctions can front with their clause; coordinating ones can't.
迷ったら意味ではなく形で選ぶ。When in doubt, choose by shape, not by meaning.