In Japanese, there are many homonyms which are words that have exactly the same reading but have different meanings. This article focuses on かく(kaku). 書く, 描く, 画く all have same reading かく(kaku) but meaning slightly differs. When you are not sure which one to use, refer to the ways to differentiate them.
書く: To write. Used when writing letters.
描く: To draw or to paint. Used when drawing pictures or diagrams in detail.
画く: To draw. Used when drawing pictures or diagrams.
As you can tell from the above description, 描く and 画く are used in almost the same way. 描く is used for drawing with fine details such as manga, but 画く is used for drawing simple pictures or diagrams. However, since 画く is not a regular kanji, today the word 描く is used for drawing pictures and diagrams. On the other hand, 書く is a word used when writing letters or sentences. As 書く cannot have meanings of to draw, 描く is used to describe the scenery or the psychology of the characters in the novels.
Examples of 書く (To write)
Tegami wo kaite okutta
I wrote the letter and sent it.
Shosetsu wo kaite oubo shita
I wrote a novel and submitted it to a competition.
Monogatari wo kakunoga sukida
I like writing stories.
Examples of 描く (To draw/paint)
Manga wo kaku
I draw manga
Eni kaita mochi
This is a Japanese idiom that has the same meaning as pie in the sky or castle in the air.
A metaphor for something that is actually of no use, or something that is unlikely to come true.
Illustrators are divided into people who prefer to draw using pen and paper and people who prefer using their PCs and tablets.
Examples of 画く(To draw)
Sen wo kaku
Draw a line
I draw graphs and tables for a document for presentation
Since this is a kanji outside of the regular usage, it is basically written as 描く instead of 画く. If you are not sure whether to use 書く, 描く or 画く, just remember that you should use 書く to write characters, 描く to draw pictures or diagrams in details, and 画く to paint pictures or diagrams. If you are not sure between 描く and 画く, use 描く because it’s more commonly used and can be used as 画く anyway.