I'll answer the question right up front. Technically, a keyword is always a keyword. Well, I hope you enjoyed this article! Until next time...
If only it was that easy. Lightroom has a very powerful keywording system. With power comes both flexibility and complication. There are types of keywords. Some will not appear in Lightroom's keyword list but can be included in the image. Others will appear in the list but not be included in the image. Confusing? Yes. Useful? Very! So let's start at the beginning and look at the three types of keywords Lightroom has.
The first type is a category keyword. These keywords are not meant to be included in the image but serve as hierarchy dividers. Like chapters in a book. If you create this type of keyword outside of Lightroom enclose it in square brackets as shown above. It is a good practice to make your categories all uppercase since Lightroom gives no indication that a keyword in the list is a category.
To create a category in Lightroom click the + at the top of the Keyword List panel.
In the dialog that follows, enter the name of the category. The important thing to do if you want a category is to make sure that the Include on Export checkbox is unchecked. When you are done press the create button.
The new category now appears in the keyword list.
I did mention that Lightroom does not indicate which keywords are categories. As you can see that's not entirely true. Categories are shown in brighter text whether or not they have any images associated with them but only if they contain other keywords. However, since other keywords are shown in brighter text as soon as they are assigned to an image this distinction becomes useless. So for all practical purposes, Lightroom does not indicate which are categories. Hopefully this will be addressed in a future version. For now I recommend that you use all uppercase for your category names.
These are the keywords we all know and love! Plain and simple descriptions that help us find our images. When creating keyword lists outside of Lightroom these keywords are typed as is. No brackets and no braces. They can be at the top of the hierarchy and stand by themselves or included further down the hierarchy.
There are two easy ways to create a keyword in Lightroom. The first is to click the + at the top of the Keyword List panel. The dialog that follows should be familiar.
This time you want to be sure that the Put inside "xxxxx" checkbox is unchecked. That will create a top level keyword. If you check that box it will put the new keyword in the hierarchy.
The other way to add a keyword is by typing it in the Click here to add keywords field of the Keywording panel. This, by default, will add top level keywords. Unlike the first method, these keywords are immediately assigned to the selected images. If no images are selected this field is unavailable.
These keywords are the workhorses of Lightroom keywording.
The last type of keyword is a synonym. Outside of Lightroom these are created by enclosing them in curly braces. Synonyms are very powerful but very confusing since they don't appear in the keyword list. However, if you look back at my previous article Just Add a Touch of Synonym! you can see how these fit into keywording.
Synonyms can only be created in Lightroom while creating (or editing) a keyword. Just add them to the Synonyms field separated by commas.
After you press the edit (or create) button your synonyms are in the keyword database. But they do not appear in the list.
However, you can filter and search with synonyms! Useful, yet confusing.
This has been a basic introduction to keywords in Lightroom. In the next keywording article I'll take a look at what keywords wind up where and when they get there.