Word pairs like 嫉妒/忌妒 with similar pronunciations and meanings - examples and discussion please

Question

I was thinking about how slight changes in pronunciation are reflected in writing.

As a case in point, here are two examples of words whose pronunciations are different, but similar, and whose meaning is the same. (Based on a few dictionaries like ABC and 现代汉语规范词典).

嫉妒 ji2du4 / 忌妒 ji4du5 
Verb: be jealous of; hate

Is this a regional variation? Or is it the case that some people will sometimes use one pronunciation, and sometimes the other, depending on the context or on their mood?

嘟囔 du1nang5 / 嘟哝du1nong5
Verb: mutter/mumble to oneself
The entry in现代汉语规范词典 for 嘟哝 says现在一般写作“嘟囔”.

Does anyone really make a distinction between du1nang5 and du1nong5? Is there an audible difference? And, if the answer is yes, then how about answers to the questions I asked regarding the "jealous" pair?

This phenomenon could be called “synonyms that are nearly, but not quite, homophones”. I would be interested in other examples. Are there any other notable ones? I have a feeling there may well be around a dozen examples commonly used in 普通话. (Still, as an intermediate student I realise I may well be wrong.)

(A related phenomenon is two different pronunciations of the same character, where each pronunciation has the same or similar meaning. But to limit the scope of this question, I’m leaving out that topic here.)

Are there any articles/discussions about this sort of topic? Ideally they would be in English, and not be too scholarly. But maybe that's too much to hope for...!

I found a related question: Two-character homonyms with same meaning which is about variant spellings (异形词). This question is a little bit different I think. I'm interested in when the pair are considered to be two separate words, but whose meaning is the same (or almost the same).

Edit: I just came across another pair, 按 and 摁. They're not synonyms, but the meanings are still quite close.

Edit 2 (2018-04-03): This question is about pairs of words/terms (词) where the pronunciation is similar but different and the meaning is the same, or close. An attempt at saying it in Chinese: 同义或近义，音近但是不一样的词.

Here is another example: 直爽—直率. Also, I found two other candidates but I'm not sure if they qualify, as the difference in meanings may be a bit too much:

扩大—夸大
挣钱—赚钱

Edit 3 (2018-04-05): Just noticed another example (贫困—贫苦). I think it may be helpful to keep this question up to date with lists of all the examples I'm aware of.

Synonyms / 同义词：嫉妒—忌妒，嘟囔—嘟哝，贫困—贫苦，堵塞—阻塞

Similar (but distinct) meanings / 近义词：按—摁，直爽—直率，挣钱—赚钱

Answer 1

First, as a native speaker I can tell you, the usage of these 异形词 is not dependent on regions or moods(at least to my observation), instead it is purely semantic or conventional.

Second, it is very unfortunate that, although some of the pairs are totally interchangeable, like the “嘟囔-嘟哝” pair you mentioned, but some are NOT. Some pairs of 异形词 DO have similar but different meanings, these differences usually lie in emotional tendencies, and some are used to describe different things, and in some pairs one word suggests different information than the other one does.

By the way, Chinese high school test paper makers like to use such pairs to baffle students, here’s a classic one:

煊赫(xuān hè) 烜赫(xuan3 hè) 显赫(xian3 hè)

They all say one is very famous, or one’s social status is very distinguished, the difference is the former two are somewhat disapproval, and the last one is neutral and most widely used.

You mentioned 直爽-直率, they do have a similar meaning but they are used to describe different things. “直爽” is used to describe a kind of personality, “直率” is used to describe a style of speech (that is direct and frank). So you can say a “直率” way of speech is included in a “直爽的” personality. But yeah they can interchange.

Also, in some pairs, words carry different information. For example: 贫困-贫苦have a similar meaning, but the former one means only “poor”, the latter not only “poor” but also “live a bitter life”. 挣钱-赚钱 both mean “to earn money”, but the former one emphasizes “to earn money with labor, work and struggle”, the latter one means merely “to get money”. To this end, we say:

投资股票非常赚钱。Investing in stocks is very profitable.

我要努力挣钱。I must struggle to earn money.

In this kind of situation usually it’s OK to interchange but the result might look weird to a native speaker.

Some pairs mean very differently. In 不负(fù)众望-不孚(fú)众望, the former means “one did not fail people’s expectations”, but the latter means exactly the opposite: “one failed people’s expectations”.

Finally, there isn’t a set of rules to which one can decide whether a pair is interchangeable or not, but luckily in most cases people can understand you, and if you expose yourself enough to these ambiguities, slowly you can tell the differences.

Answer 2

In our country, what you called is noted as:
异形词 it include:{
同音异体same tone differy body
同义异体 same meaning different body} it is edited as an excel

http://xh.5156edu.com/page/z1858m3646j18784.html but i don't think you should memorize,what you should do is familar with the “近义词”

嫉妒 ji2du4 / 忌妒 ji4du5
it is quite same，when you use in oral spoken,it is always changeable,we commonly use 忌妒,but when you use in paper or some more strict occasion, it has some different,嫉妒 it target is beyond us 忌妒 it is someone who has something i don't have .

嘟囔 du1nang5 / 嘟哝du1nong5 it is different tone

嘟囔

http://hanyu.baidu.com/zici/s?wd=嘟囔&query=嘟囔%20读音&srcid=28236&from=kg0&from=kg0

嘟 哝≈弄

http://hanyu.baidu.com/zici/s?wd=嘟哝&query=嘟哝读音&srcid=28236&from=kg0&from=kg0

in the end you say 按 and 摁
It is called 近义词 it is commonly used ，you should practice a lot to know it when you want to know the word same meaning ，you just search 百度
eg：好 近义词 or use 百度知道