grammar - Unifying concept for noun-adjectives of the pattern Xかな

Consider these:

• 
  

  静か

  
  


• 
  

  愚か

  
  


• 
  
  

  厳か

  
  

• ～やか:

• 
  
  

  穏やか

  
  


• 
  

  鮮やか

  
  


• 
  

  賑やか

  
  

• ～らか:

• 
  

  柔らか

  
  


• 
  

  滑らか

  
  
  


• 
  

  明らか

  
  

There are many more that I've not listed.

The か/やか/らか at the end of these words seem to suggest that they stem from a common grammar construct. What is it? And does it mean anything?

Answer

In short, -raka and -yaka are compound of -ra + -ka and -ya + -ka, respectively. -ra, -ya, and -ka are all derivational suffixes that add a stative sense.

-ya is rather rare. In the Old Japanese corpus, I can only find three words: nikoya, nagoya, and fuwaya. This suggests that suffix was of only limited productivity then and explains why it was soon supplemented by -ka resulting in -yaka.

-ra attaches to adjective stems, nominals, and sounds. Ex: akara, mahora, simira, utura. During Old Japanese, more productive than -ya, but that declined as time when on. This too was supplemented by -ka resulting in -raka.

-ka Derivatives are often adverbial or the stem of 形容動詞. Ex: isasaka, oroka, sayaka, sizuka, niwaka, honoka. This same -ka is often attached to -ya and -ra.

Also note that there are two other related suffixes: -sa and -ma.

-ma: Attaches to adjectival stems, nominals, the irrealis form of verbs, negative -zu etc. awazuma ni, kaerama ni, kotosima, sakasima, futuma ni, yokosima.

-sa: Attaches to adjectival stems creating nouns. Still productive. Rarely also attaches to nouns as well: tatasa, yokosa. Also joins with -ma to create -sama, which suggests an intriguing etymology for 様 (sama).