影 vs 形 vs 形状. What's the difference between them?


I've been reading a text and all three of these come up 影 vs 形 vs 形状. I know
they mean shape/figure, but is there a more nuanced difference between them? I
can see the logic of where they are in the text but I can't figure out the
difference.




If you are familiar with the general difference between on-readings (音読み) and
kun-readings (訓読み), you already know the basic difference between 形【かたち】 (kun)
and 形状【けいじょう】 (on).

  * 形 is used in informal conversations/writings and most of formal conversations, while 形状 is preferred in formal written texts or scientific articles.
  * Usually Japanese children learn 形【かたち】 first, and many Japanese idioms are based on 形【かたち】. (形作【かたちづく】り、形【かたち】をなす、形【かたち】から入る、形【かたち】ばかりの、...)
  * 形状 is frequently combined with other 音読み words to form longer phrases, as in 形状記憶合金 (shape-memory alloy).

The primary meaning of 影【かげ】 is _shadow_ or _silhouette_ , not _shape_ , in
modern Japanese. A few certain words, such as 月影【つきかげ】, contain 影 to mean
_shape_ , but I think such usage is archaic or poetic.

> 地図で見ると、イタリアは長靴のような形をしている。 : OK (Casual)  
>  地図で見ると、イタリアは長靴のような形状をしている。 : OK (Formal)  
>  (*)地図で見ると、イタリアは長靴のような影をしている。: Incorrect (at least in modern Japanese)




If you are familiar with the general difference between on-readings (音読み) and
kun-readings (訓読み), you already know the basic difference between 形【かたち】 (kun)
and 形状【けいじょう】 (on).

  * 形 is used in informal conversations/writings and most of formal conversations, while 形状 is preferred in formal written texts or scientific articles.
  * Usually Japanese children learn 形【かたち】 first, and many Japanese idioms are based on 形【かたち】. (形作【かたちづく】り、形【かたち】をなす、形【かたち】から入る、形【かたち】ばかりの、...)
  * 形状 is frequently combined with other 音読み words to form longer phrases, as in 形状記憶合金 (shape-memory alloy).

The primary meaning of 影【かげ】 is _shadow_ or _silhouette_ , not _shape_ , in
modern Japanese. A few certain words, such as 月影【つきかげ】, contain 影 to mean
_shape_ , but I think such usage is archaic or poetic.

> 地図で見ると、イタリアは長靴のような形をしている。 : OK (Casual)  
>  地図で見ると、イタリアは長靴のような形状をしている。 : OK (Formal)  
>  (*)地図で見ると、イタリアは長靴のような影をしている。: Incorrect (at least in modern Japanese)

