What is a secondary word?

When Josh Wordle (yes, that's his name) created his game, he pulled a list of some 13,000 words from a database (I don't know which) and had his girl friend pull out the words that could be the guess of the day. The rejected words would be valid guesses, but would never be the word of the day.

Regular plurals, like "NOUNS", stayed in the secondary list.

Regular past tenses, like "VOWED", stayed in the secondary list.

Regular adjectivizations of nouns, like "MISTY", stayed in the secondary list.

Obscure words that show up only in scrabble games, like "AALII", stayed in the secondary list.

Josh's girl friend is British, so there's a British bias in the primary word list, although it contains both British and American spellings. Anything to get another word in the list.

And Lirdle inherited this list. I moved some of the words from one list to the other to make it more suited to worldwide, English-knowledgeable solvers. I also assumed that it wasn't asking too much to expect the average Lirdle player to have done high school science, and moved about 10 science-related words from the secondary list to the primary ("AXION" showed up recently, probably the most obscure of those words).

But the culling isn't perfect. Once the first round of Lirdle goes through the complete list of primary words, sometime in 2028, if anyone is still playing it I'll go through the two lists more closely and try to make the qualities that make a word primary more consistent, but this is always going to be subjective.