Labels
Words which are used only or mainly in one region or country are marked:

BrE British English
AmE American English
AusE Australian English

Words which are used in a particular situation, or show a particular attitude:

approving a word that is used to praise things or people, although this may not be clear from its meaning
disapproving a word that is used to show dislike or approval, although this may not be clear from its meaning
formal a word or phrase that is suitable for formal speech or writing, but would not normally be used in everyday conversation
informal a word or phrase that is used in normal conversation, but may not be suitable for use in more formal contexts, for example in writing essays or business letters
humorous a word that is normally used in a joking way

Words which are used in a particular context or type of language:

biblical a word or phrase that is used in the language of the Bible, and would sound old-fashioned to a modern speaker
law a word or phrase with a technical meaning used by lawyers, in legal documents etc
literary a word or phrase used mainly in English literature, and not in normal speech or writing
medical a word or phrase that is more likely to be used by doctors than by ordinary people, and that often has a more common equivalent
not polite a word or phrase that is considered rude, and that might offend some people
old-fashioned a word or phrase that was commonly used in the past, but would sound old-fashioned today
old use a word or phrase used in earlier centuries
spoken a word or phrase used only, or nearly always, in conversation
taboo a word or phrase that should not be used because it is very rude or offensive
technical a word or phrase used by doctors, scientists, and other specialists
trademark a word or phrase that is the official name of a particular product
written a word or phrase that is used only, or nearly always, in written English