Comparative Glyph Origins Of (Visually) Close Characters

Question

As part of my learning experience, I am taking the useful advice someone offered and examining the many different tools available to learn more characters. To that effect, I am keying in the characters into a Mac using pinyin. I noticed that there are a number of visually related characters with different meanings. Is this a known phenomenon or just an unusual coincidence?

Some examples are:

天，夭

>

失，矢

I noticed that the differences are so slight (at least to my untrained eye) that one wonders about the glyph origins and how these visually related characters came to be. Is there a science to these visual relationships or are they random?

EDITS: Added to the examples with links to Chinese Etymology and Zhongwen images. However, I am still unsure of whether the development of the characters is related. I also plugged the characters into zdict.net but I am not competent enough to understand whether there is an explanation that might help me answer the main question: 天，夭，失，矢

Answer 1

They are not much related.

The common part in these characters is 大/big, which is the pictograph of front of a person.

天 is sky, which is represented by the line above the person.

夭's original meaning is bending one's neck, represented by a curve on person's head.
It's extended meaning is "young", because young plants are curved.

The other two are different.

矢 is arrow. The top part is head and the bottom part is arrow feather.

失 is very interesting. It actually comes from 手/hand with a extra stroke.
Something falls out of one's hand -> lose something