One of my favourite little touches in macOS: Look Up
And don’t forget that you can add look up support for Emoji symbols using my Emojipedia Dictionary.
On iOS (since version 10) and macOS (since 10.5 Leopard) there’s a feature called Data Detectors that helps recognise various forms of data in text, such as phone numbers, street addresses, contacts, and so on.
A simple version of this is the use of capitalised words as markers to detect phrases during Look Up. It’s not foolproof, as we can see in my video, but it works well more often than not.