What are ways to create "simplifed" Chinese characters?

Question

Most Chinese characters have two parts, a radical and a phonetic. So different ways to simplify them might include the following:

1) Simplify the radical, retain the phonetic. Example: 调

2) Simplify the phonetic, retain the radical. Example: 这

3) Simplify one or the other of the above, for a character that has only one, but not the other. Example: 车

4) Substitute a single "character" for both parts. Example: 后

Is this roster complete? One way that I haven't seen is that both the radical and phonetic are simplified. Is this true, and if so, why might that be?

Answer 1

Wikipedia's Simplified Chinese page has a section that outlines all the types already. Quoting it a bit:

There are four methods used:

Structural simplification of characters

Under this method, there are the following:

• Replacing a character with another existing character that sounds the same or similar (e.g. 乾、幹 → 干)

• Using printed forms of cursive shapes (e.g. 長 → 长)

• Replacing a component of a character with a simple symbol (e.g. 對 → 对)

• Omitting entire components (e.g. 習 → 习)

• Further morphing a character after omitting some components (e.g. 歸 → 归)

• Preserving the basic outline or shape of the original character (e.g. 飛 → 飞)

• Replacing the phonetic component of phono-semantic compound characters (e.g. 鐘 → 钟)

• Replacing some arbitrary part of a character with a phonetic component, turning it into a new phono-semantic compound character (e.g. 曆 → 历)

• Replacing entire character with a newly coined phono-semantic compound character (e.g. 驚 → 惊)

• Adopting obscure ancient forms or variants (e.g. 電 → 电)

• Adopting ancient vulgar variants (e.g. 陽 → 阳)

• Re-adopt abandoned phonetic-loan characters (e.g. 後 → 后)

Derivation based on simplified character components

This is where components that have been simplified are also simplified when they are used as radicals; e.g. 單 → 单 so therefore 彈 → 弹

Elimination of variants of the same character

E.g. 夠 → 够, 豬 → 猪. Note that the goal here is to reduce the total number of characters, which means that sometimes the simplified version has more strokes, e.g. 搾 → 榨

Adoption of new standardized character forms

E.g. 奧 → 奥, 虛 → 虚. These are structurally the same after simplification.

For more information see https://zh.wikisource.org/zh/%E7%AE%80%E5%8C%96%E5%AD%97%E6%80%BB%E8%A1%A8