Which of these words is considered non-standard: 늘, 항상, 늘상?

Answer: 늘상

늘 is the pure Korean word for always, and 항상 (恒常) is the Sino-Korean word for always, and both appear in my dictionaries, but 늘상 does not appear in my dictionaries because it is considered a non-standard word.

늘상 is a combination of the pure Korean word 늘 (always) and the Chinese character 常 (상), which means always and is one of the characters in 항상 (恒常), the Sino-Korean word for always. In other words, 늘상 is redundant because it literally means always, always. Actually, 항상 (恒常) is also redundant because it also literally translates as always (恒), always (常), but the redundancy in 항상 (恒常) is necessary because if you were to say either 항 or 상 by itself in a sentence, Koreans would most likely not understand you. However, if you were to say 늘 in a sentence, Koreans would understand you, so adding 상 (常) to it is unnecessary. In fact, 늘 is the only one-syllable word in my dictionaries with the sound /늘/, so there is almost no way Koreans would confuse it with another word.

The reason I am writing about this is that I just saw 늘상 used in a book written by Ko Jong-seok (고종석), who is a former reporter, novelist, and linguist. The title of the book is 국어의 풍경들 (Views of the Korean Language), a very interesting book that talks about different aspects of the Korean language, including the redundancy of many Korean words and expressions. I just thought it was ironic that a Korean linguist like Mr. Ko Jong-seok would choose to use 늘상 instead of either 늘 or 항상 in a book about the Korean language. Actually, 늘상 should have been one of his examples in his article about redundancy in the Korean language.

Here is the sentence from the book:

그러나 이 언어들은 비록 독립된 언어와 방언의 경계가 늘상 또렷한 것은 아니지만, 프랑스어의 방언이 아니라 엄연히 독립된 언어들로 인정되고 있다.