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)