「however」には主な意味が二つあり、それぞれ、「but」そして「in whatever way」と同義です。前者の場合には「 however 」は必ず副詞ですが、以下が示すように誤って接続詞として使用されていることをしばしば目にします。
- [誤] I would like to go to a movie, however I have no money.
- [正] I would like to go to a movie, but I have no money.
- [正] I would like to go to a movie. However, I have no money.
- [誤] The argument given in Ref.  may be correct, however it is not convincing.
- [正] The argument given in Ref.  may be correct, but it is not convincing.
- [正] The argument given in Ref.  may be correct. However, it is not convincing.
- [正] Although/While/ the argument given in Ref.  may be correct, it is not convincing.
Compared to other hydrofunctionalization methods, however, transition metal-catalyzed hydrothiolation is relatively underexplored, likely due to sulfur’s strong coordinating ability and ensuing catalyst deactivation.
Over 160 chiral vicinal bromochlorinated natural products have been identified; however, a lack of synthetic methods for the selective incorporation of halogens into organic molecules has hindered their synthesis. 引用：10.1021/jacs.5b08398
There was good agreement between our observations and computational predictions. No reaction or low yields were seen for substrates 7a–7e (entries 1–5). However, when the calculated DG and the oxidative addition barrier were favourable, substantial formation of product 8a was observed (entries 6 and 7) 引用：10.1038/nature14615